PURPOSE: To prevent lubricant from entering a compressor of a heat gas engine having a plurality of cylinders, by constituting a compressor with the cylinders which are respectively communicated to two operating spaces corresponding to different phases of a heat gas engine.

CONSTITUTION: Displacers 1a, 1b, 1c, and 1d are installed inside cylinders 2a, 2b, 2c, and 2d so that they may slide. A primary operating space 3b is communicated to a heater 5b, while a secondary operating space 4b is communicated to a cooler 6b. The heater 5b is connected to the cooler 6c. The cooler 6c is also connected to the secondary operating space 4c of another cylinder 2c through a regenerating heat exchanger 7b. The primary space 10 in a cylinder 8 is communicated to the primary operating space 3a while the secondary space 13 is communicated to the primary operating space 3b. With this construction, a compressor 17 operates with differential phases of the displacers 1a and 1b.