This power module has: a copper layer comprising copper or a copper alloy, provided on a circuit layer (12) surface bonded to a semiconductor element (3); and a soldered layer (20) formed by using a solder material and formed between the circuit layer (12) and the semiconductor element (3). An alloy layer (21) containing Sn as the main component thereof and also containing 0.5-10 mass% Ni and 30-40 mass% Cu is formed in the interface between the soldered layer (20) and the circuit layer (12). The thickness of this alloy layer (21) is set in the range of 2-20 [mu]m, and has a thermal resistance increase rate of no more than 10% in a power cycle test in which the power cycle under conditions of a temperature difference of 80 DEG C and a conduction duration of 5 s is set to a load of 100,000 times.