A semiconductor module includes a fixed type and transformable type coolers and a flat semiconductor package sandwiched between the coolers. A relative positional relationship of the semiconductor package is fixed with the fixed type cooler, but variable with the transformable type cooler. The transformable type cooler includes a transformable member of a metal thin plate covering a coolant chamber. The semiconductor module includes a sandwiching mechanism causing the fixed type cooler to be pressed toward the transformable type cooler. Fastening adjustment screws of the sandwiching mechanism causes a pressing frame to approach a cooler body of the transformable type cooler. Therefore, the semiconductor package is pressed via the fixed type cooler while the transformable member is slightly transformed. This enhances a degree of contact between the semiconductor package and transformable member via an insulating member.