Yield curves of sand in a particle-crushing region were determined by the multi-step stress path method with a high pressure triaxial apparatus. The yield curves depicted on the p-q diagram were found to have such characteristics as dq/dp=G(η), irrespective of stress path, where q is deviator stress, p is mean principal stress, and η is stress ratio. Integrating the dq/dp～η curve numerically, the η-U_p(η) relationship was obtained, by which a family of yield curves was constructed. It was shown that the yield curves of a family are similar with respect to the origin of the p-q diagram and hence they can be normalized so as to form a single curve by using a newly defined stress parameter p_e.