A first insulating substrate is formed on a heat sink, and a semiconductor element is formed thereon. An insulating resin casing is formed so as to cover the first insulating substrate and the semiconductor element. A second insulating substrate is mounted inside the insulating resin casing apart from the first insulating substrate. On the second insulating substrate, a resistance element that functions as a gate balance resistance is fixed by soldering. The second insulating substrate on which the resistance element was thus mounted was made apart from the first insulating substrate on which the semiconductor element was mounted, and was mounted on the side of the insulating resin casing.