A power module , comprising: a semiconductor element for converting DC current to AC current by switching operation; an electrical wiring board to which the semiconductor element is electrically connected, with the semiconductor element being disposed upon one of the principal surfaces of the electrical wiring board; an insulating resin layer provided on the other of the principal surfaces of the electrical wiring board; a first alumite layer that is formed by first alumite processing which does not include hole sealing processing, is disposed on an opposite side of the electrical wiring board from the semiconductor element, separated by the insulating resin layer, and that is joined to the insulating resin player; a second alumite layer that is formed by second alumite processing which does not include hole sealing processing, is disposed on an opposite side of the insulating resin layer from the semiconductor element, separated by the first alumite layer, and that ensures electrical insulation of the semiconductor element; and a metallic heat dissipation member that is disposed on an opposite side of the first alumite layer from the semiconductor element, separated by the second alumite layer, and that is adapted to radiate heat generated by the semiconductor element via the electrical wiring board, the insulating resin layer, the first alumite layer, and the second alumite layer, characterized in that a hole diameter of the first alumite layer is greater than a hole diameter of the second alumite layer; and a thickness of the second alumite layer is greater than a thickness of the first alumite layer. a semiconductor element for converting DC current to AC current by switching operation; an electrical wiring board to which the semiconductor element is electrically connected, with the semiconductor element being disposed upon one of the principal surfaces of the electrical wiring board; an insulating resin layer provided on the other of the principal surfaces of the electrical wiring board; a first alumite layer that is formed by first alumite processing which does not include hole sealing processing, is disposed on an opposite side of the electrical wiring board from the semiconductor element, separated by the insulating resin layer, and that is joined to the insulating resin player; a second alumite layer that is formed by second alumite processing which does not include hole sealing processing, is disposed on an opposite side of the insulating resin layer from the semiconductor element, separated by the first alumite layer, and that ensures electrical insulation of the semiconductor element; and a metallic heat dissipation member that is disposed on an opposite side of the first alumite layer from the semiconductor element, separated by the second alumite layer, and that is adapted to radiate heat generated by the semiconductor element via the electrical wiring board, the insulating resin layer, the first alumite layer, and the second alumite layer, characterized in that a hole diameter of the first alumite layer is greater than a hole diameter of the second alumite layer; and a thickness of the second alumite layer is greater than a thickness of the first alumite layer. <EOS>