PURPOSE: To work easily a rotor and also improve its working efficiency by simplifying the gear shape of the rotor, in a non-contact rotary machine.

CONSTITUTION: The low pressure side impeller side surface (line c") of an impeller 1 is created toward the recessed part 12 of a female rotor by only the creating curve surface (line 1") of a projection, and a rotor is rotated while maintaining a clearance (about 1 to 2mm in normal condition) which is sufficiently large relatively in comparison with a sealing clearance between a part or the whole of wall surface from the impeller outer circumferential side end part of a part created by the creating curve surface (line 1") of the impeller 1 till the whole range of the impeller outer circumferential surface 1', and the wall surface (line L') of the bottom part of the recessed part 12.