A benzenesulfonate salt of (2S,4S)-2-cyano-4-fluoro-1-[(2-hydroxy-1,1-dimethyl)ethylamino]acetylpyrr- olidine that has an excellent DPPIV inhibition activity as well as physical properties (e.g., stability) required for pharmaceutical preparations. The present invention allows easy obtaining of the compound in high-purity uniform crystal form with excellent solid-state stability.