PROBLEM TO BE SOLVED: To provide a rotor which cools a core body while inhibiting fragments of a magnet from flying out when the magnet is damaged.SOLUTION: Multiple lightening hole parts 25 are formed so as to be arranged in a circumferential direction of a core body 20 and penetrate through the core body 20 in a plate thickness direction. Multiple magnets 30 are provided on an outer wall 26 of the core body 20 so as to be arranged in the circumferential direction of the core body 20. A cylindrical member 40 is provided at the radial outer side of the core body 20 so that an inner wall contacts with the magnets 30. A plate member 50 is provided so as to close one end and the other end of the cylindrical member 40. Hole parts 52 are formed at positions which correspond to the lightening hole parts 25 of the plate member 50 so as to penetrate through the plate member 50 in the plate thickness direction.