A type 2 crystal of 2-(3-ethanesulfonylpyridin-2-yl)-5-(trifluoromethanesulfonyl)benzoxazole having diffraction peaks at 2θ=14.0±0.2°, 14.3±0.2°, 16.5±0.2°, 16.9±0.2°, 17.6±0.2°, 18.8±0.2°, 19.9±0.2°, and 22.3±0.2° in powder X-ray diffraction using Cu-Kα radiation is a stable crystal.