The present invention provides monomethanesulfonate of phenylpyrrole derivatives, having excellent glucokinase activating activity, significantly improving solubility, hygroscopicity and stability, and exhibiting excellent oral absorption, and the crystal thereof. The present invention provides (2S) -2- (3- {5- [(5S) -5- Methyl -4, 5-dihydro-1, 3-oxazol-2-yl]-1H-pyrrol-2-yl}-5-{[5-(methylsulfonyl ) pyrazin-2-yl] oxy} phenoxy) propan-1-ol monomethanesulfonate, having excellent glucokinase activating activity, the crystal thereof, a medicine comprising them, and a prophylactic and/ or therapeutic agent for diabetes, etc.
