A water-based solid lubricant includes water, glycerin, isoalkane, molybdenum disulfide, talc powder, calcium sulfonate, and polyisobutylene is described herein.

To provide a grease-sealed bearing that is superior in fretting wear resistance and sealing performance when used under an oscillation condition with acceleration and deceleration such as a condition used in a robot joint. A grease-sealed bearing 1 includes an inner ring 2 and an outer ring 3 that are raceway rings, a plurality of rolling elements 4 interposed between the inner ring 2 and the outer ring 3, and a grease composition 7 sealed around the rolling elements 4. The bearing oscillates such that a bearing rotational direction changes while accelerating and decelerating. The grease composition contains a base oil and a thickener. The worked penetration of the grease composition is 310 or more. The thickener is a calcium sulfonate complex soap.