To simplify structure, to form an intake system in a compact manner, and to recover energy.

This intake system comprises a fluid machine 9 arranged in an intake flow passage 5; a generator-motor 11 to drive the fluid machine 9; a battery 13 to feed a power to the generator-motor 11; an accelerator pedal angle sensor 17; a number of revolutions of engine sensor 19; and a controller 15 to receive signals from the sensors 17 and 19, rotate the fluid machine 9 through the generator-motor 11 by the battery 13 according to an accelerator pedal angle, the number of revolutions of an engine, or the differential values of the above or charge the battery 13 by the power of the generator-motor 11 driven by the fluid machine 9.