A reciprocating compressor includes a front frame; a middle frame positioned with an interval from the front frame; an outer stator having a winding coil and coupled between the front frame and the middle frame; a cylinder coupled to the front frame; a magnet mounting inner stator having a protruded pole portion at both ends thereof and linear-movably inserted into the outer stator; a magnet mounted at an outer circumferential surface of the magnet mounting inner stator; a piston inserted into the cylinder; a connection unit for connecting the piston and the magnet mounting inner stator; a resonance spring unit for resonating the piston and the magnet mounting inner stator; and a valve assembly for opening and closing a gas flow path so that gas can be sucked into the cylinder and compressed as the piston is linearly-reciprocated. According, the amount of the expensive magnet used is reduced, an output of a driving motor is enhanced, and components are simplified.