A manufacturing method for a power module capable of shortening a manufacturing time for a power module is obtained. The manufacturing method for a power module includes: a subassembly arranging step of placing a subassembly including a first electrode, a semiconductor device, and a second electrode on a heat sink via a joining material; and a transfer molding step of, after the subassembly arranging step, under a state in which the first electrode, the semiconductor device, and a second-electrode inner portion are arranged in a region surrounded by the heat sink and a molding die, injecting a thermoplastic resin into the region, wherein, in the transfer molding step, the subassembly is joined to the heat sink via the joining material with use of the resin.