A heat-sink-attached-power module substrate (1) has a configuration such that either one of a metal layer (13) and a heat sink (31) is composed of aluminum or an aluminum alloy, and the other one of them is composed of copper or a copper alloy, the metal layer (13) and the heat sink (31) are bonded together by solid phase diffusion bonding, an intermetallic compound layer formed of copper and aluminum is formed in a bonding interface between the metal layer (13) and the heat sink (31), and an oxide is dispersed in an interface between the intermetallic compound layer and either one of the metal layer (13) composed of copper or a copper alloy and heat sink (31) composed of copper or a copper alloy in a layered form along the interface.