In a rotor structure of a permanent magnet type rotary machine comprising a cylindrical permanent magnet 3 fixed on an outer peripheral surface of a rotor shaft 2, wherein torque acting on the permanent magnet 3 is transmitted to the rotor shaft 2, the rotor structure further comprises two annular side plates 4 and a holding ring 5. Each side plate has an axial hole 4a into which the rotor shaft 2 is fitted so as to rotate with the side plates integrally and the side plates 4 are attached on the both end surface of the permanent magnet 3, respectively so as to confront with each other. A circular U-shaped groove 4c coaxially with the axial hole 4a is provided at a end surface 4b for facing with the permanent magnet 3 of each side plate 4. The holding ring 5 is formed cylindrically and covers circumferential sections of the permanent magnet 3 and the side plates 4 and fasten the permanent magnet 3 and the side plates 4 so as to move them integrally.