The purpose of the present invention is to provide a semiconductor substrate manufacturing method, which prevents detachment of a semiconductor wafer being ground, and which prevents cracking or chipping in a semiconductor substrate obtained. In order to solve the problem, the semiconductor substrate manufacturing method comprises: a polyimide layer forming step of forming a polyimide layer on a support material; a wafer attaching step of affixing the support material and a semiconductor wafer to each other with the polyimide layer disposed therebetween; a wafer grinding step of grinding the semiconductor wafer; a support material peeling step of peeling the support material from the polyimide layer; and a polyimide layer peeling step of peeling the polyimide layer from the semiconductor wafer. The polyimide layer includes polyimide which includes a benzophenone skeleton and an aliphatic structure, wherein an amine equivalent weight is 4000 to 20000.