In an outer circumferential portion of an intermediate partition plate, a concave portion is provided at a position at which an upper vane and a lower vane slide. At a lower dead center of an upper piston and a lower piston, 80% or more of the entire length in the sliding direction of the upper vane and the lower vane are accommodated respectively on the inside of an upper cylinder and the inside of a lower cylinder. In the concave portion, a width W with respect the circumferential direction of the intermediate partition plate is greater than a thickness T of the upper vane and the lower vane, and when a depth of the concave portion is D and the entire length of the upper vane and the lower vane is L, D≥0.1×L is satisfied.