A scroll compressor, comprising: a casing having a sealed inner space (112,113); a drive motor provided in the inner space of the casing to generate a rotational force; a rotating shaft coupled to a rotor of the drive motor to rotate; an orbiting scroll coupled to the rotating shaft to perform an orbiting movement; a fixed scroll coupled to the orbiting scroll to form a compression space consisting of a suction chamber, an intermediate pressure chamber and a discharge chamber; and a rotation prevention member (170, 270) coupled to the orbiting scroll, wherein at least part of rotation prevention member (170, 270) is formed of a different material from that of the orbiting scroll, wherein the rotation prevention member comprises: a ring portion; a plurality of key portions formed in a protruding manner on both axial-directional lateral surfaces of the ring portion to allow the rotation prevention member to be slidably coupled in a radial direction to key grooves of the corresponding member; characterised in that thrust surfaces are formed in a protruding manner on the axial-directional lateral surfaces of the ring portion, and a stepped surface is formed at both sides in circumferential direction of the thrust surface to form a weight loss portion on the axial-directional lateral surfaces of the ring portion. a casing having a sealed inner space (112,113); a drive motor provided in the inner space of the casing to generate a rotational force; a rotating shaft coupled to a rotor of the drive motor to rotate; an orbiting scroll coupled to the rotating shaft to perform an orbiting movement; a fixed scroll coupled to the orbiting scroll to form a compression space consisting of a suction chamber, an intermediate pressure chamber and a discharge chamber; and a rotation prevention member (170, 270) coupled to the orbiting scroll, wherein at least part of rotation prevention member (170, 270) is formed of a different material from that of the orbiting scroll, wherein the rotation prevention member comprises: a ring portion; a plurality of key portions formed in a protruding manner on both axial-directional lateral surfaces of the ring portion to allow the rotation prevention member to be slidably coupled in a radial direction to key grooves of the corresponding member; characterised in that thrust surfaces are formed in a protruding manner on the axial-directional lateral surfaces of the ring portion, and a stepped surface is formed at both sides in circumferential direction of the thrust surface to form a weight loss portion on the axial-directional lateral surfaces of the ring portion. a ring portion; a plurality of key portions formed in a protruding manner on both axial-directional lateral surfaces of the ring portion to allow the rotation prevention member to be slidably coupled in a radial direction to key grooves of the corresponding member; characterised in that thrust surfaces are formed in a protruding manner on the axial-directional lateral surfaces of the ring portion, and a stepped surface is formed at both sides in circumferential direction of the thrust surface to form a weight loss portion on the axial-directional lateral surfaces of the ring portion.