PURPOSE: To enable heat transfer efficiency to be enhanced and a pressure drop of working fluid to be reduced, by providing inside a spacer a flow path for the second fluid to flow and performing a heat exchange between the first and second fluids even in a spacer part.

CONSTITUTION: The first working fluid 21 of high pressure helium gas or the like is fluidized reciprocating through space 18 surrounded by a heat transmitting pipe 11 and a spacer 12 which are positioned between a regenerative heat exchanger and a compression cylinder. While the second cooling fluid 22 of water or the like is allowed to flow in the heat exchanger from its one end inlet 23 and along the outside of the heat transmitting pipe 11 then to the outside from an outlet 24 in the other end. Further one part of the second fluid 22 is allowed to flow in an internal flow path 14 of the spacer 12 from a hole 16 of the heat transmitting pipe 11 and to the outside from a hole 17 and the outlet 24. Here the first and second fluids 21, 22 are isolated by flanges 25, 26, and the second fluid 22 is allowed to flow in the vicinity of the heat transmitting pipe 11 by a partitioning member 27. In this way, the heat exchanger enables the improvement of heat transfer efficiency, reduction of a pressure drop of working fluid, decrease of ineffective volume, improvement of workability, etc. to be attained.