To easily assemble permanent magnets being kept in an engaged state into the body of a rotor and to keep the positional relationship between the basic magnets and the auxiliary magnets even after assembling jig is removed, by forming an even number of first permanent magnets in and the same even number of second permanent magnets in such a shape that they may be engaged with each other.

2M (M is a positive even number) basic magnets 2 are formed with a recessed section 2b which allows the basic magnets 2 to engage with auxiliary magnets 3. On the inner side of the basic magnets 2 and the auxiliary magnets 3, the body 1a of a rotor and a rotary shaft 1x of a rotor are formed. Due to this structure, a rotor 1 can be assembled with the minimum influence from a repulsive force or an attractive force between the magnetized permanent magnets caused by their magnetic forces. Even after an assembling jig is removed, the permanent magnets never deviate in position and therefore the position of the combined magnet rotor can be kept as it is.