Provided with an insulation circuit board in which a circuit layer is joined to one side of a ceramic substrate and a metal layer made of aluminum or aluminum alloy is joined to the other side of the ceramic substrate, and a heat sink joined to the metal layer; the heat sink has a first metal layer made of copper joined to the metal layer, a ceramic board material joined to the first metal layer at an opposite side to the metal layer, and a second metal layer made of copper or copper alloy joined to an opposite side of the ceramic board material to the first metal layer; and a thickness T1 of the first metal layer is 0.3 mm to 3.0 mm inclusive and equal to or more than a thickness T2 of the second metal layer.