To provide a method and a device for highly efficiently converting heat into kinetic energy with a simple structure.

After heating a working medium in a second operation chamber 3a of a first heat exchanger 1a by the equal volume by a heat transfer medium supplied to a first operation chamber 2a of the first heat exchanger 1a, at least a part of the working medium is transferred to the second operation chambers 3b and 3c of separate heat exchangers 1b and 1c of a rear stage from the second operation chambers 3a and 3b of the heat exchangers 1a and 1b of a front state including this first heat exchanger 1a, and the working medium in the second operation chambers 3b and 3c of the rear stage heat exchangers 1b and 1c is heated by the equal volume by the heat transfer medium in first operation chambers 2b and 2c of the rear stage heat exchangers 1b and 1c, and this working medium is supplied to an air pressure-oil pressure converter 17, and a hydraulic medium is discharged from the converter 17.