A cryogenic refrigerator includes a displacer having a flow channel that supplies a refrigerant gas to a regenerator; and a cylinder that accommodates the displacer so as to be movable in an axial direction, has a heat diffusion portion at a high-temperature end portion thereof, and forms a space portion together with a high-temperature end of the displacer. A clearance is formed between an outer peripheral surface of the displacer and an inner peripheral surface of the cylinder. The flow channel is made to open to the outer peripheral surface of the displacer, and the refrigerant gas within the room-temperature chamber flows into the regenerator through the clearance and the flow channel.