diff --git a/hostr/cmd/tools/resolvePubKey.go b/hostr/cmd/tools/resolvePubKey.go
new file mode 100644
index 0000000..e3732dd
--- /dev/null
+++ b/hostr/cmd/tools/resolvePubKey.go
@@ -0,0 +1,24 @@
+package tools
+
+import (
+	"fmt"
+
+	"github.com/nbd-wtf/go-nostr/nip19"
+)
+
+func ResolvePubKey(npubOrHex string) (string, error) {
+	// npubから始まる場合はデコードする
+	if npubOrHex[0:4] == "npub" {
+		_, v, err := nip19.Decode(npubOrHex)
+		if err != nil {
+			return "", fmt.Errorf("Invalid npub")
+		}
+		return v.(string), nil
+	} else {
+		_, err := nip19.EncodePublicKey(npubOrHex)
+		if err != nil {
+			return "", fmt.Errorf("Invalid pubkey")
+		}
+	}
+	return npubOrHex, nil
+}