To solve the problem associated with conventional electromagnetic devices that movements of magnets in the radial direction are difficult to control and high-speed rotation cannot be achieved.

An electromagnetic device has a stator extending along the axis in the direction of length, and the stator has an inner surface which defines a rotor housing recess. A rotor is extended along the axis so that the rotor can rotate around the axis in the direction of length in the rotor housing recess. A plurality of ring assemblies are supported on the rotor, and a plurality of magnets are separated from one another around the rotor in the circumferential direction and extended through the ring assemblies. Each magnet is placed in parallel with the axis of the rotor.