A rotor of an electric motor, including a rotor core having a plurality of magnet-retaining apertures, a plurality of permanent magnets individually received and retained in the magnet-retaining apertures of the rotor core, and a resinous filler filling a gap defined between each magnet-retaining aperture and each permanent magnet and fixing the permanent magnets to the magnet-retaining apertures. The rotor also includes an engaging projection provided in the rotor core, the engaging projection tightly engaged with each of the permanent magnets received in the magnet-retaining apertures and temporarily holding each permanent magnet at a predetermined position in a corresponding magnet-retaining aperture, in an unfinished state of the rotor where the resinous filler is not arranged in the gap.