The objective of the present invention is to provide: a crystal having high purity and excellent properties (such as stability and solubility) of a highly safe compound with few side effects, said compound having μ-opioid receptor antagonist activity； and a method for producing this crystal. A crystal of a salt or hydrate thereof, said salt being composed of a compound represented by formula (I) and an acid selected from the group consisting of hydrochloric acid, hydrobromic acid and oxalic acid. (In the formula, R
