A PCU has an inside sealed by a case made of aluminum and a bottom plate. Interior space of the PCU accommodates an IPM, a control substrate, and a capacitor. The IPM is provided to abut an upper surface of the bottom plate. The control substrate is a rectangular plate having mounted thereon a control circuit including electronic components such as a gate driver, a transformer and the like, and is provided above the IPM. The capacitor is accommodated in a housing in a substantially parallelepiped form. A reflector made of aluminum of high thermal reflectivity and high thermal conductivity is provided on the entire lower surface of the capacitor.