diff --git a/kadai1/imgconv/.gitignore b/kadai1/imgconv/.gitignore
new file mode 100644
index 0000000..723ef36
--- /dev/null
+++ b/kadai1/imgconv/.gitignore
@@ -0,0 +1 @@
+.idea
\ No newline at end of file
diff --git a/kadai1/imgconv/Makefile b/kadai1/imgconv/Makefile
new file mode 100644
index 0000000..f8aa0c8
--- /dev/null
+++ b/kadai1/imgconv/Makefile
@@ -0,0 +1,4 @@
+.PHONY: fmt
+fmt: ## Format source code
+	@which goimports > /dev/null || GO111MODULE=off go get -u golang.org/x/tools/cmd/goimports
+	@goimports -d -w $(shell find . -type f -name '*.go')
\ No newline at end of file
diff --git a/kadai1/imgconv/cmd/imgconv/main.go b/kadai1/imgconv/cmd/imgconv/main.go
new file mode 100644
index 0000000..d341cf2
--- /dev/null
+++ b/kadai1/imgconv/cmd/imgconv/main.go
@@ -0,0 +1,34 @@
+package main
+
+import (
+	"flag"
+	"log"
+	"os"
+
+	"github.com/gopherdojo/dojo7/kadai1/sabe/pkg/imgconv"
+)
+
+func main() {
+	if err := exec(); err != nil {
+		log.Println(err)
+		os.Exit(1)
+	}
+	os.Exit(0)
+}
+
+func exec() error {
+	var (
+		dir     string
+		fromExt string
+		toExt   string
+	)
+	flag.StringVar(&dir, "d", ".", "target directory flag")
+	flag.StringVar(&fromExt, "f", "jpg", "before convert ext flag")
+	flag.StringVar(&toExt, "t", "png", "after convert ext flag")
+	flag.Parse()
+	imageConfList, err := imgconv.NewImageConfList(dir, fromExt, toExt)
+	if err != nil {
+		return err
+	}
+	return imageConfList.Convert()
+}
diff --git a/kadai1/imgconv/go.mod b/kadai1/imgconv/go.mod
new file mode 100644
index 0000000..e876026
--- /dev/null
+++ b/kadai1/imgconv/go.mod
@@ -0,0 +1,3 @@
+module github.com/gopherdojo/dojo7/kadai1/sabe
+
+go 1.12
diff --git a/kadai1/imgconv/go.sum b/kadai1/imgconv/go.sum
new file mode 100644
index 0000000..5726ce0
--- /dev/null
+++ b/kadai1/imgconv/go.sum
@@ -0,0 +1 @@
+github.com/gopherdojo/dojo7 v0.0.0-20190903074013-69385d40c994 h1:UbdhtSFDdFiSYOb/TkEmlRIUFQRrBlKOzVDY3+SXaSw=
diff --git a/kadai1/imgconv/imgconv b/kadai1/imgconv/imgconv
new file mode 100755
index 0000000..ced1033
Binary files /dev/null and b/kadai1/imgconv/imgconv differ
diff --git a/kadai1/imgconv/pkg/imgconv/convert.go b/kadai1/imgconv/pkg/imgconv/convert.go
new file mode 100644
index 0000000..fe88315
--- /dev/null
+++ b/kadai1/imgconv/pkg/imgconv/convert.go
@@ -0,0 +1,32 @@
+package imgconv
+
+import (
+	"image/gif"
+	_ "image/gif"
+	"image/jpeg"
+	_ "image/jpeg"
+	"image/png"
+	_ "image/png"
+)
+
+func (l ImageConfList) Convert() error {
+	for _, v := range l {
+		err := v.Convert()
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (imgCf ImageConf) Convert() error {
+	switch imgCf.ToExt {
+	case "png":
+		return png.Encode(imgCf.ToFile, imgCf.DecodedFile)
+	case "gif":
+		return gif.Encode(imgCf.ToFile, imgCf.DecodedFile, nil)
+	case "jpg", "jpeg":
+		return jpeg.Encode(imgCf.ToFile, imgCf.DecodedFile, nil)
+	}
+	return nil
+}
diff --git a/kadai1/imgconv/pkg/imgconv/main.go b/kadai1/imgconv/pkg/imgconv/main.go
new file mode 100644
index 0000000..fc9ceae
--- /dev/null
+++ b/kadai1/imgconv/pkg/imgconv/main.go
@@ -0,0 +1,115 @@
+package imgconv
+
+import (
+	"fmt"
+	"image"
+	"io"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+type ImageConf struct {
+	FromExt     string
+	ToExt       string
+	DecodedFile image.Image
+	ToFile      io.Writer
+}
+
+type ImageConfList []ImageConf
+
+// create ImageConfList
+func NewImageConfList(dir, fromExt, toExt string) (ImageConfList, error) {
+	// read dir
+	paths, err := readDir(dir, strings.ToLower(fromExt))
+	if err != nil {
+		return nil, err
+	}
+	imgCfList := make(ImageConfList, len(paths))
+	for i, path := range paths {
+		imgCf := ImageConf{
+			FromExt: strings.ToLower(fromExt),
+			ToExt:   strings.ToLower(toExt),
+		}
+
+		// set decode file
+		err = imgCf.SetDecodedFile(path)
+		if err != nil {
+			return nil, err
+		}
+
+		// set output file
+		err = imgCf.SetToFile(getConvertedPath(path, strings.ToLower(toExt)))
+		if err != nil {
+			return nil, err
+		}
+
+		imgCfList[i] = imgCf
+	}
+	return imgCfList, nil
+}
+
+// set ImageConf.DecodedFile
+func (imgCf *ImageConf) SetDecodedFile(path string) (err error) {
+	// open file
+	file, err := os.Open(path)
+	if err != nil {
+		return
+	}
+	defer func() {
+		err = file.Close()
+	}()
+
+	// decode file
+	img, _, err := image.Decode(file)
+	if err != nil {
+		return
+	}
+	imgCf.DecodedFile = img
+	return
+}
+
+// set ImageConf.ToFile
+func (imgCf *ImageConf) SetToFile(path string) error {
+	// create output file
+	toFile, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	imgCf.ToFile = toFile
+	return nil
+}
+
+//  recursively read directory
+func readDir(dir, fromExt string) ([]string, error) {
+	files, err := ioutil.ReadDir(dir)
+	if err != nil {
+		return nil, err
+	}
+
+	var paths []string
+	for _, file := range files {
+		if file.IsDir() {
+			paths2, err := readDir(filepath.Join(dir, file.Name()), fromExt)
+			if err != nil {
+				return nil, err
+			}
+			paths = append(paths, paths2...)
+			continue
+		}
+		extStart := strings.LastIndex(file.Name(), ".")
+		if extStart > 0 && strings.ToLower(file.Name()[extStart+1:]) == fromExt {
+			paths = append(paths, filepath.Join(dir, file.Name()))
+		} else {
+			continue
+		}
+	}
+	return paths, nil
+}
+
+// get converted file path
+func getConvertedPath(path, toExt string) string {
+	extStart := strings.LastIndex(path, ".")
+	return fmt.Sprintf("%s.%s", path[:extStart], toExt)
+}
diff --git a/kadai1/imgconv/testutils/testdata/test.jpg b/kadai1/imgconv/testutils/testdata/test.jpg
new file mode 100644
index 0000000..fe679aa
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diff --git a/kadai1/imgconv/testutils/testdata/test.png b/kadai1/imgconv/testutils/testdata/test.png
new file mode 100644
index 0000000..66b47c7
Binary files /dev/null and b/kadai1/imgconv/testutils/testdata/test.png differ