A reciprocating compressor is provided. Bearing holes of a fluid bearing of the compressor may be positioned correspond to a full reciprocating region of a piston, to reduce/eliminate frictional loss and/or abrasion between a cylinder and the piston. The bearing holes may be concentrated at certain regions of the cylinder to stably support the piston through a full reciprocating range. Compression coil springs may maintain concentric alignment of the cylinder and the piston. Gas through holes may be radially formed at the piston to lower a pressure of a bearing space and allow refrigerant to be smoothly introduced into the bearing space through a gas pocket. A casing of the compressor may include an outer shell and an inner shell to attenuate vibration generated due to friction generated by operation of the reciprocating compressor.