Disclosed is a motor fixing structure of a reciprocating compressor comprising: a front frame having a predetermined shape; a middle frame positioned with a certain interval from the front frame; an outer stator positioned between the front frame and the middle frame so that an inner stator can be positioned with a certain interval therein; a coupling means for fixing the outer stator positioned between the front frame and the middle frame by coupling the front frame and the middle frame to each other; and a sliding preventing means installed between the outer stator and the front frame contacting each other and/or between the outer stator and the middle frame contacting each other for preventing sliding. According to this, a motor assembly is simplified, and abrasion and damage of components are prevented by preventing a motor assembly dimension variation during driving.