diff --git a/src/Data/ByteString/ToolsYj.hs b/src/Data/ByteString/ToolsYj.hs
--- a/src/Data/ByteString/ToolsYj.hs
+++ b/src/Data/ByteString/ToolsYj.hs
@@ -7,7 +7,7 @@
 
 	fromBits, fromBits', toBits, toBits',
 
-	toBitsBE
+	fromBitsBE', toBitsBE
 
 	) where
 
@@ -37,3 +37,9 @@
 
 toBitsBE :: Bits b => BS.ByteString -> b
 toBitsBE = BS.foldl (\s b -> bitsToBits 8 b .|. s `shiftL` 8) zeroBits
+
+fromBitsBE' :: FiniteBits b => b -> BS.ByteString
+fromBitsBE' b0 = go (finiteBitSize b0 `div` 8) b0
+	where
+	go 0 _ = ""
+	go n b = go (n - 1) (b `shiftR` 8) `BS.snoc` bitsToBits 8 b
diff --git a/tools-yj.cabal b/tools-yj.cabal
--- a/tools-yj.cabal
+++ b/tools-yj.cabal
@@ -5,7 +5,7 @@
 -- see: https://github.com/sol/hpack
 
 name:           tools-yj
-version:        0.1.0.27
+version:        0.1.0.28
 synopsis:       Tribial tools
 description:    Please see the README on GitHub at <https://github.com/YoshikuniJujo/tools-yj#readme>
 category:       Tools