Disclosed is a power module having improved joint reliability. Specifically disclosed is a power module including a power module substrate wherein a circuit layer is brazed on the front surface of a ceramic substrate, a metal layer is brazed on the rear surface of the ceramic substrate and a semiconductor chip is soldered to the circuit layer. The metal layer is composed of an Al alloy having an average purity of not less than 98.0 wt. % but not more than 99.9 wt. % as a whole. In this metal layer, the Fe concentration in the side of a surface brazed with the ceramic substrate is set at less than 0.1 wt. %, and the Fe concentration in the side of a surface opposite to the brazed surface is set at not less than 0.1 wt. %.