A gas leakage preventing apparatus for a rotary compressor comprises: a cylinder having a cylindrical inner space therein; a rotating shaft having an eccentric portion therein which makes a circular motion in the inner space of the cylinder; a rolling piston inserted into the eccentric portion of the rotating shaft and being linearly contact with an inner wall of the inner space of the cylinder; a vane linear-movably inserted into a vane slot which is formed in the cylinder and dividing the cylinder inner space together with the rolling piston; and fixing units provided in the rolling piston and vane, for restraining a rotary motion of the rolling piston. As a result, it is possible to maximize gas compression efficiency by minimizing leakage of high pressure gas