A power module has a copper layer composed of copper or a copper alloy on a surface of a circuit layer to which a semiconductor device is bonded, and a solder layer that is formed by using a solder material is formed between the circuit layer and the semiconductor device. An average crystal grain size which is measured by EBSD measurement in a region having a thickness of up to 30 μm from the surface of the circuit layer in the solder layer is 10 μm or less, the solder layer has a composition that contains Sn as a main component, 0.01 to 1.0% by mass of Ni, and 0.1 to 5.0% by mass of Cu, and a thermal resistance increase rate when a power cycle is loaded 100,000 times is less than 10% in a power cycle test.