Rotary compressor

A rotary compressor equipped with a compression unit having: a ring-shaped cylinder; an end plate for closing the end section of the cylinder, and having a shaft-receiving part and a discharge-valve part; a ring-shaped piston for engaging the eccentric part of a rotating shaft supported by the shaft-receiving part, revolving inside the cylinder along the inner wall thereof, and forming a working chamber between itself and the inner wall of the cylinder; and a vane for projecting into the working chamber from within a vane groove of the cylinder, contacting the ring-shaped piston, and dividing the working chamber into an intake chamber and a compression chamber. Therein, the vane is formed from a steel material and has a diamond-shaped carbon layer on the surface which slides with the ring-shaped piston, and the ring-shaped piston is formed from Ni-Cr-Mo iron to which 0.15-0.45 wt% of phosphorus has been added, or is formed from iron or steel and has an iron nitride layer formed on the outer-circumferential surface thereof.