An electric motor (20) has a stator (30) and a rotor (26). The latter is equipped with a cup-like rotor part (56) and with a ring magnet (60) adhesively bonded therein, which magnet has an outer circumference (61) on which are provided elevations (84) and depressions (86) that extend at least partly in the longitudinal direction of the ring magnet (60). The outer circumference (61) of the ring magnet (60), that faces toward the cup-like rotor part (56) after assembly, is formed with at least one opening or channel (68; 69, 88), extending in a circumferential direction, that is connected to at least a plurality of the flat depressions (86). Positive mechanical engagement between adhesive and ring magnet enhances durability, and discourages any tendency toward relative rotation between the magnet (60) and the cup-like rotor part (56).