A rotor 6 includes a rotor core 610, and a plurality of magnets 620 arrayed on the rotor core 610 in its circumferential direction at center angles of equal intervals. Given an axial length L of the rotor core 610, a radial length D of the rotor core 610, and a thickness t of the magnets 620, the following relationships are satisfied: L/D (1K)/(L 1.5 DP) (wherein P is the number of poles, K is 100000, and N is a factor that depends on the output of the compressor). Thus, while torque decreases due to large reduction in rotor layering thickness is suppressed, a small-size, lightweight and low-priced compressor motor is provided.