This structural member design method is a method for designing a structural member obtained by forming a tailored blank. The method includes: a weld setting step of performing crash analysis by numerical simulation on an analytical model of the structural member, and setting the position of the weld such that a fracture index of a first region is equal to or more than a specified value and the fracture indices of all remaining regions other than the first region are less than the specified value; and a removal region setting step of setting, after the weld setting step, a region including a portion corresponding to the first region in the joined end portion as a removal region where the exposed portion is formed.