The present invention provides a crystal of 1-{2-[(3S,4R)-1-[(3R,4R)-1-cyclopentyl-3-fluoro-4-(4-methoxyphenyl)pyrrolidine-3-carbonyl]-4-(methoxymethyl)pyrrolidin-3-yl]-5-(trifluoromethyl)phenyl}piperidine-4-carboxylic acid having a certain quality that can be used as a drug substance. Specifically, the present invention provides a crystal comprising an equimolar amount of 1-{2-[(3S,4R)-1-[(3R,4R)-1-cyclopentyl-3-fluoro-4-(4-methoxyphenyl)pyrrolidine-3-carbonyl]-4-(methoxymethyl)pyrrolidin-3-yl]-5-(trifluoromethyl)phenyl}piperidine-4-carboxylic acid and phosphoric acid.