Disclosed is a crystal of 2-hexadecyloxy-6-methyl-4H-3, 1-benzoxazin-4-one useful as a preventative 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 power 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 ± 0.2λ.
