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.