Disclosed is a crystal of 2-hexadecyloxy-6-methyl-4H-3,1-benzoxazin-4-one useful as a preventive or therapeutic agent for obesity and the like. Specifically disclosed is a crystal of 2-hexadecyloxy-6-methyl-4H-3, 1-benzoxazin-4-one having a powder X-ray diffraction pattern in which characteristic peaks appear at powder X-ray diffraction interplanar spacings (d) of around 16.54±0.2, 13.26±0.2, 4.70±0.2, 4.38±0.2, and 3.67±0.2A.
