Crystal of 5-chloro-6-[(2- iminopyrrolidin-1-yl)methyl]pyrimidine-2,4(1H,3H)-dione monohy¬d¬ro¬¬chloride having characteristic peaks at diffraction angles (2θ ± 0.1˚) of 11.6˚, 17.2˚, 17.8˚, 23.3˚, 27.1˚ and 29.3˚ in powder X-ray diffraction, and pha¬r¬maceutical composition on a basis thereof. Table: 3