A hypoid gear tooth surface design method, wherein normal lines and helical angles of two tooth surfaces are properly selected so as to position action limit curves (L3Acc) on the outer of the areas (R2t to R2h) where the tooth surfaces are formed, whereby undercut to a gear small end side can be prevented and, by setting the involute helicoids of two tooth surfaces on a pinion side to an equal lead, a pinion top land and a gear top land (z2hnull0) can be made generally equal to each other in tooth lengthwise direction, such that sharpening of the top land can be prevented.