Two insulation covers that can be vertically separated clamp a gate-driving-circuit substrate so as to form a gate driving apparatus. The gate driving apparatus is fixed to a cooler by fixing screws inserted through a pair of insertion bores in the two insulation covers that are arranged in a horizontal direction. A gate control terminal and a ground control terminal provided on the gate-driving-circuit substrate are screwed and fixed to, and thus electrically and mechanically connected to, a corresponding gate control terminal and a corresponding ground control terminal of a power module attached to the cooler. This allows the gate-driving-circuit substrate to be covered with the insulation covers for insulation protection and to be fixed to the cooler using a fixing member such as a screw.