A magneto rotor which has a cup-like rotor yoke, a plurality of magnets secured on an inner periphery of a peripheral wall portion of the rotor yoke, and a magnet protecting cover having a cylindrical portion that covers inner peripheries of the magnets, and an outer flange being integrated with one axial end of the cylindrical portion and covering end surfaces of the magnets, wherein an annular protrusion protruding toward the opening of the rotor yoke is formed on an area closer to an inner periphery of the outer flange of the magnet protecting cover, an annular adhesive storage portion is formed between the peripheral wall portion closer to the open end of the rotor yoke and the annular protrusion, a groove opening into the adhesive storage portion and continuing circumferentially of the rotor yoke is also formed in the peripheral wall portion closer to the open end of the rotor yoke, and the adhesive storage portion and the groove are filled with an adhesive to seal a boundary between the outer flange of the magnet protecting cover and the peripheral wall portion of the rotor yoke with the adhesive.