1. A method for evaluating bone comprising the steps of: (a) determining a bone pattern (i) by measuring the photodensity of an X-ray photograph of the long bone of a limb or (ii) by photon absorptiometry from the long bone of a limb; (b) smoothing and symmetrizing the bone pattern to modify the same; (c) determining a bone density distribution by setting a bone model having an elliptic bone cross-sectional external shape, a zonate bone cortex, and a bone density decreasing portion in the inside of the bone cortex from the modified bone pattern; and (d) evaluating the bone based on the bone density distribution.