To provide a main motor bearing that can extend a grease life.

A main motor bearing 90 for a railway vehicle supports a main motor spindle on a member disposed so as to face the outer peripheral surface of a main spindle, a main spindle being rotatably supported about the axis. The main motor bearing 90 includes: an outer ring 91 having an outer ring rolling surface 91a provided on the inner peripheral surface thereof; an inner ring 92 having an inner ring rolling surface 92a on the outer peripheral surface thereof and disposed on the inside of the outer ring 91 so that the inner ring rolling surface 92a faces the outer ring rolling surface 91a; rolling bodies 93 which are in contact with both the outer ring rolling surface 91a and the inner ring rolling surface 92a and which are arranged side-by-side on the annular path; and a retainer 94 which retains the rolling bodies 93 at a predetermined pitch in the circumferential direction. The rolling bodies 93 are ceramic balls. The retainer 94 consists of a resin.