To provide a motor capable of realizing high reliability and facilitating size reduction.

A flange portion 322, expanding in the vertical direction to a central shaft J1, is provided at a substantially cylindrical sleeve-retaining portion 32 for retaining a sleeve 31, and an inclination surface 323, of which the diameter gradually reduces toward a lower side from the flange portion 322 is formed at the outer periphery surface of the sleeve-retaining portion 32. A substantially cylindrical yoke 23 on the central shaft J1 side of a field magnet 24 is provided at a rotor portion 2, and a boundary face of lubricating oil is formed in a gap 40 in between the inclination surface 323 of the sleeve retaining portion 32 and the inner periphery surface of the yoke 23. A stopper mechanism, in which the yoke 23 is engaged with the flange portion 322 without contact, is constituted. As a result, when respective components of the motor are made small, there is no need for the stopper mechanism which is difficult to handle to be provided separately, thus facilitating size reduction for the motor, and realizing high reliability.