A rotor includes: a circular rotor core; and a plurality of θ magnets. The θ magnets are contained in a magnet holding sections such that the same magnetic pole of one magnet as that of another magnet adjacent to said one magnet faces the same magnet pole of the adjacent magnet in circumferential directions of the rotor core. Given that the number of magnetic poles of the rotor is denoted by P, the maximum outside diameter of the rotor core is denoted by Dr [mm], and the thickness of the plate-like magnet in a circumferential direction of the rotor core is denoted by Lm [mm], the following inequality (2) is satisfied: 0.665×10−4×P2−0.28×10−2×P+0.577×10−1