In a supercharger (10) with an electric motor in accordance with the invention, an inner side of the center housing (10) is provided with an air introduction path (38) introducing a part of a compressed air within the compressor housing (8) to the electric motor (20), and a cooling structure portion (40) cooling the air flowing through the air introduction path (38). The center housing (14) has a cooling fluid flow path (34) which is formed so as to surround the electric motor (20) and puts a cooling fluid for cooling the electric motor (20) in circulation inside. The cooling structure portion (40) is structured such as to be capable of heat exchanging between the cooling fluid and the air flowing through the air introduction path (38).