Degradation rate is suppressed to be low by suppressing the occurrence of structural defects. Provided is an implant manufacturing method including a molding step (S1) of molding a molded item by treating a raw-material piece constituted of a biodegradable metal material with plastic processing and a grain-size adjusting step (S2) of increasing metal grain size by applying a heat treatment to the molded item molded in the molding step (S1).
