A power module can prevent damages due to cracking or breakage of an insulating substrate when molding even if a heat plate constituting a power module pre-product is made areally smaller than the insulating substrate, and can also sufficiently satisfy demand for minimization. Specifically, the power module pre-product is sealed by a molding resin layer in a state where externally exposed end portion on one end side in both external connecting terminals and the other surface side of a heat plate are each exposed to the outside. The power module substrate constituting a multilayer substrate body includes an aligning hole, into which an aligning pin is inserted, the pin being included in a lower molding die constituting a molding die with an upper molding die that molds a molding resin layer, so as to position the power module pre-product inside a cavity.