A highly stable crystal of (1S)-1,5-anhydro-1-[5-(4-{(1E)-4-[(1-{[2-(dimethylamino)ethyl]amino}-2-methyl-1-oxopropan-2-yl)amino]-3,3-dimethyl-4-oxobut-1-en-1-yl}benzyl)-2-methoxy-4-(propan-2-yl)phenyl]-D-glucitol, and a process for producing the crystal are provided. Specifically, an ethanolate having the following physical properties, and a plurality of other crystal forms transformed from the ethanolate are provided: (a) Having peaks at. 2¸ = 5.9 degrees, 17.1 degrees, 17.6 degrees and 21.5 degrees in X-ray powder diffraction (Cu-K±)； (b) Showing characteristic absorption bands at 3538 cm -1 , 3357 cm -1 , 2964 cm -1 , 1673 cm -1 , 1634 cm -1 and 1505 cm -1 in an infrared absorption spectrum； and (c) Having a melting point in a vicinity of 111°C.
