PURPOSE: To simplify a driving system in relation to a rotating machine capable of suppressing frictional loss and wear at blade tips.

CONSTITUTION: A fixed piston 3 is disposed in an opening 4a formed at a turning cylinder 4, and a compression chamber 5 is formed between the fixed piston 3 and the turning cylinder 4. Blades 8a-8d are mounted to the turning cylinder 4, and the end parts of the blades 8a-8d are inserted through in the blade through-holes 3a-3d of the fixed piston 3 so as to partition the compression chamber 5 into small compression chambers 5a-5d. Electromagnets 13a-13d are disposed around the turning cylinder 4. The electromagnetic force thereof is controlled to make the turning cylinder 4 perform turning motion around the fixed piston 3, and thereby the small compression chambers 5a-5d are contracted to compress refrigerant. The structure of a driving system is simplified by thus utilizing the electromagnetic force as turning driving force.