To make improvements in lubricity and durability by eliminating any effect of the inclination of a motor's washer receiving surface to the washer of a thrust bearing.

A large washer 25 having an outer diameter being larger than that of a thrust surface of a bearing 12 and a small washer 25a being smaller than the former are set up so as to mark this small washer 25a upwards, whereby even if a washer receiving part of a rotor 10 is inclined to some extent, the large washer 25 comes into contact with the thrust surface with no inclination, so that a uniform flow of lubricating oil is well promoted and any possible partial contact or the like is not produced, besides durability is improved.