A rotor (30) comprises a rotor core (31) having electromagnetic steel sheets laminated, six permanent magnets (32) buried axially in the rotor core (31) and arranged substantially in a regular hexagonshape in the circumferential direction, rivets (33) arranged near and radially inside of the apexes of the regular hexagon formed of the six permanent magnets (32), and extending therethrough in theaxial direction to fasten the rotor core (31), and through holes (34) formed between the rivets (33) of the rotor core (31) and extending axially through the rotor core (31). The through holes (34) are formed in the rotor core (31) radially inside of the central portions of the permanent magnets (32).