An acoustic fluid machine includes an acoustic resonator, a valve device, a piston, and an actuator. The acoustic resonator has a larger-diameter base and a smaller-diameter upper end. The valve device is provided on the upper end of the acoustic resonator and has a sucking hole and a discharge hole. The piston is provided in the base of the acoustic resonator and has a surface such that the distance between the upper end of the acoustic resonator and the upper surface of the piston is substantially constant over the whole surface of the piston. The actuator is connected to the piston and reciprocates the piston at high speed axially with a very small amplitude so that a gas is sucked into the acoustic resonator via the sucking hole and discharged via the discharge hole by virtue of pressure fluctuations within the acoustic resonator.