PURPOSE: To prevent a ring-shaped magnet from being deviated and use the ring-shaped magnet commonly as a magnetic pole to be detected.

CONSTITUTION: In a DC brushless motor 10 where a plurality of ring-shaped magnets 17 and 18 are engaged to the outer periphery of a rotor shaft 15 to constitute a rotor 14 and Hall elements 24 oppose on one end face of the rotor 14, a recessed part 19 and a projecting part 20 are formed and engaged each other on the butt surface of a first magnet 17 and a second magnet 18 and the Hall elements 24 oppose the projecting part 20 of the second magnet 18, thus mechanically connecting the first magnet 17 and the second magnet 18 due to the engagement of the recessed part 19 and the projecting part 20 and hence preventing the magnetization patterns between both magnets from being deviated and achieving the initial output of a motor. Since the projecting part 20 of the second magnet 18 can be utilized for the magnetic pole to be detected, the number of parts and assembly man-hour can be reduced.