An object of the present invention is to provide a crystal of trans-3-amino-1-methyl-3-(4-(3-phenyl-5H-imidazo[1,2-c]pyrido[3,4-e][1,3]oxazin-2-yl)phenylcyclobutanol having excellent stability and favorable characteristics in terms of its production and formulation into drugs. The present invention provides a crystal of trans-3-amino-1-methyl-3-(4-(3-phenyl-5H-imidazo[1,2-c]pyrido[3,4-e] [1,3]oxazin-2-yl)phenylcyclobutanol having characteristic peaks of diffraction angle (2¸±0.1°) at 7.7°, 9.5°, 10.3°, 12.3°, 14.5°, 15.6°, 16.3°, 17.8°, 18.3°, 19.3°, 20.9°, 22.8°, 24.2°, 25.7°, 26.8°, 27.7°, 29.0° and 30.1° in a powder X-ray diffraction spectrum.
