A rotary-type fluid machine includes a compression mechanism having piston mechanisms arranged one on top of the other and a drive mechanism having a drive shaft that is configured and arranged to drive the piston mechanisms. Each of the two piston mechanisms includes a cylinder member with a cylinder chamber, a piston member housed eccentrically in the cylinder chamber such that the cylinder chamber is partitioned into first and second compression chambers. A phase difference of 90 degrees in volume change is made between the cylinder chambers of the two piston mechanisms. A movable one of the cylinder and piston has a first surface facing one of the first cylinder chambers and a second surface facing one of the second cylinder chambers, with a surface area of the first surface being equal to a surface area of the second surface.