A compressor comprising: a cylinder comprising a cylinder body which has a cylindrical shape, the cylinder defining a compression space for refrigerant gas; a piston configured to be reciprocated in an axial direction within the cylinder body and to compress the refrigerant gas in the compression space; and a frame in which the cylinder is received, the frame defining a gas hole, one side of the gas hole communicating with a space in which the refrigerant gas is present after the compression so that the refrigerant gas is introduced, the other side of the gas hole extending up to an inner circumferential surface thereof so as to guide the refrigerant gas, wherein the gas hole communicates with a gas pocket comprising a space between an outer circumferential surface of the cylinder and an inner circumferential surface of the frame, and wherein the cylinder comprises: a gas inlet provided in a shape of a groove recessed from the outer circumferential surface of the cylinder and communicating with the gas pocket; a nozzle extended from the gas inlet and formed to pass through the cylinder body, wherein the gas pocket communicates with an inner space of the cylinder body via the nozzle; and a porous filter member seated in the gas inlet to filter the refrigerant gas introduced into the nozzle, characterized in that the porous filter member is provided in a hollow tube shape formed in a circumferential direction of the cylinder body to define an inner passage inside the porous filter member, through which the refrigerant gas flows. a cylinder comprising a cylinder body which has a cylindrical shape, the cylinder defining a compression space for refrigerant gas; a piston configured to be reciprocated in an axial direction within the cylinder body and to compress the refrigerant gas in the compression space; and a frame in which the cylinder is received, the frame defining a gas hole, one side of the gas hole communicating with a space in which the refrigerant gas is present after the compression so that the refrigerant gas is introduced, the other side of the gas hole extending up to an inner circumferential surface thereof so as to guide the refrigerant gas, wherein the gas hole communicates with a gas pocket comprising a space between an outer circumferential surface of the cylinder and an inner circumferential surface of the frame, and wherein the cylinder comprises: a gas inlet provided in a shape of a groove recessed from the outer circumferential surface of the cylinder and communicating with the gas pocket; a nozzle extended from the gas inlet and formed to pass through the cylinder body, wherein the gas pocket communicates with an inner space of the cylinder body via the nozzle; and a porous filter member seated in the gas inlet to filter the refrigerant gas introduced into the nozzle, characterized in that the porous filter member is provided in a hollow tube shape formed in a circumferential direction of the cylinder body to define an inner passage inside the porous filter member, through which the refrigerant gas flows. a gas inlet provided in a shape of a groove recessed from the outer circumferential surface of the cylinder and communicating with the gas pocket; a nozzle extended from the gas inlet and formed to pass through the cylinder body, wherein the gas pocket communicates with an inner space of the cylinder body via the nozzle; and a porous filter member seated in the gas inlet to filter the refrigerant gas introduced into the nozzle, characterized in that the porous filter member is provided in a hollow tube shape formed in a circumferential direction of the cylinder body to define an inner passage inside the porous filter member, through which the refrigerant gas flows.