A production method for a flexible semiconductor substrate according to the present invention includes: a step of providing an inorganic substrate 11; a step of forming a polyimide layer 22a on the inorganic substrate by using a material in solution form, the polyimide layer 22a having a thickness of less than 10 μm; a step of forming a semiconductor device on the polyimide layer; a step of, after forming the semiconductor device, removing the polyimide layer from the inorganic substrate; and a step of forming a polyparaxylene resin layer 35, 37 having a thickness which is equal to or greater than the thickness of the polyimide layer. The polyparaxylene resin layer may be formed on the semiconductor device before the removing step, or formed on the opposite side of the polyimide layer from the semiconductor device after the removing step. The production method according to the present invention excels in mass producibility.