The invention relates to a magnet rotor. The interior periphery of the cup-shaped rotor magnet yoke is fixed with a plurality of magnets which are provided with a magnet protection cover which, as a whole, has a barrel-shaped part covering the interior periphery of the magnets and an outer flange part which is formed at an end of the axes direction of the barrel-shaped part and covers the end faces of the magnets. An annular protruding part which protrudes to the opening of the rotor magnet yoke is formed at a part close to the interior periphery of the outer flange of the magnet protection cover. An annular adhesive storage part is formed between a periphery part close to the opening end of the rotor magnet yoke and the annular protruding part. Besides, in the periphery part close to theopening end of the rotor magnet yoke, a continuous slot is formed at the inner opening of the adhesive storage part and along the periphery of the rotor magnet yoke. The adhesive storage part and theslot are filled with an adhesive which seals the outer flange part of the magnet protection cover and the periphery part of the rotor magnet yoke.