from the inner surface 32 a and the virtual extension line lb from the inner surface 32 b when the rotor is viewed in the axial direction therefore the air layer is sufficiently provided between the permanent magnets 30 a and 30 b this suppresses a reduction in torque also the inner surface of the groove g spreads in the radially outward direction thus the distance between the projections 23 a and 23 b is greater in the radially outward direction next variations will be described fig4 a to 5c are explanatory views of variations of the projections and grooves additionally similar components will be designated with similar reference numerals and the duplication descriptions thereof will be omitted here as illustrated in fig4 a the length of projections 23 a 1 and 23 b 1 of the magnetic body 20 in the radial direction is smaller than each thickness of the permanent magnets 30 a and 30 b thus the projections 23 a 1 and 23 b 1 respectively abut with parts of bases of the side surfaces 33 a and 33 b and respectively expose the remaining parts of the side surfaces 33 a and 33 b also a bottom b 1 of the groove g 1 formed between the projections 23 a 1 and 23 b 1 is located radially inward with respect to the virtual extension lines la and lb such a shape of the groove g 1 suppresses a reduction in.