To provide a high-speed servo motor which is of such structure that the peripheral face of a magnet provided at a rotor is fastened, and is free of such a fear that the magnet is broken even if it rotates at ultrahigh speed, and therefore is suitable for a motor for a machine tool or a vacuum pump requiring ultrahigh-speed revolution.

This is a high-speed servo motor of such structure that the peripheral face of a permanent magnet 3 attached to a rotor 1 is covered with a metallic ring 4 having high tensile strength, and that the permanent magnet 3 is fastened to the rotor 1. The metallic ring 4 is one where a plurality of rings whose long face dimensions in the axial direction of the rotor are required small dimensions are put side by side, and the end face of the ring is coated with a nonconductive film, or a nonconductive collar 5 is provided between the rings so that it may minimize the occurrence of an induced eddy current or occurrence of heat generation.