Inside of a gas-tight housing, an electric motor, an inverter and a compressor are housed. Further, an intake air pipe is connected to the gas-tight housing. Inside of the gas-tight housing, an intake air flow passage is formed. Further, a connection opening of an outside air induction pipe provided with a flow rate regulating valve is arranged so as to face a suction opening of a compressor. When the delivery air flow rate as well as the delivery air pressure of the compressor is reduced due to the pressure loss and the like of the intake air ‘a’ which passes through the air flow passage and cools the electric motor and the inverter, an outside air ‘o’ of low temperature is induced so that: the capacity shortage as well as the performance deterioration of the compressor is constrained; and the over-heating of the compressor is constrained.