A capacity varying rotary compressor is provided. The compressor includes a cylinder mounted in a casing, and a vane pressure chamber provided at a rear side of a vane that divides an inner space of the cylinder into a suction chamber and a compression chamber. A pressure controlling unit supplies a discharge pressure or a suction pressure to the vane pressure chamber to thereby restrict or release a motion of the vane. A pressure leakage preventing unit couples the cylinder and bearings positioned at opposite sides of the cylinder to form the vane pressure chamber. A capacity to compress and discharge a refrigerant may be varied according to a load, thereby reducing power consumption of the compressor and simplifying assembly. Furthermore, pressure leakage from the vane pressure chamber may be prevented, thereby enhancing a capacity varying function.