A radiator having a radiator fin sandwiched between and joined to a top plate and a bottom plate is provided on an insulating substrate, which has a semiconductor element arranged on one face side thereof, on the other face side thereof. The radiator fin is a corrugated fin that includes a first region that includes a joint peak portion joined to the bottom plate and has a height in an amplitude direction which is substantially equal to a distance between the top plate and the bottom plate, and a second region that includes a non-joint peak portion separated from the bottom plate by a predetermined gap and has a height in the amplitude direction which is smaller than the distance between the top plate and the bottom plate.