According to the present invention, a grease layer having a grease as a constituent material is provided in a filling region lying between a heat dissipation surface that is a bottom surface of a heat dissipation material of a semiconductor module and a surface of a cooler. Further, a seal material is formed on the surface of the cooler and covers the entire side surface region of the grease layer without any gap. The seal material has a liquid curable sealing agent as a constituent material.