Abstract: A low-temperature end of a pulse tube (1) and a low-temperature end of a cold accumulator (2) are communicated with each other through an endothermic connection passage (3), so that refrigerant gas to be supplied from a compressor (7) to a high-temperature end of the cold accumulator (2) through a refrigerant gas passage (28) is introduced from the low-temperature end of the pulse tube (1) to the high-temperature end thereof through the cold accumulator (2) and the endothermic connection passage (3). A buffer tank (30) is connected to the high-temperature end of the pulse tube (1) through a first orifice (31). A sub gas passage (32) branched off from the refrigerant gas passage (28) is connected to the the buffer tank (30) through a second orifice (33).