In a semiconductor module 10 in which a semiconductor device 17 is mounted on both surfaces of a circuit board 11 and heat radiation plates 12a, 12b are provided to both surfaces of the circuit board to cover the semiconductor device, a fitting hole via which the heat radiation plates 12a, 12b are fitted is formed in the circuit board 11, and a housing recess portion 18 in which the semiconductor devices 11 are housed is provided to both heat radiation plates 12a, 12b fitted to both surfaces of the circuit board 11 respectively and a fitting edge portion 25 is provided in a position of both heat radiation plates that overlaps with a position in which the fitting hole is formed, and also a fixing means 20 for fixing both heat radiation plates 12a, 12b to the circuit board 11 by caulking to align with the fitting hole is provided to fitting edge portions 25 integrally with the heat radiation plates 12a, 12b.