To provide a grease composition which can maintain a molybdate in the grease composition in the dispersed state of fine particles and has excellent abrasion-resistant properties under high surface pressure and a grease-sealed roller bearing sealed with the grease composition.

The grease composition is obtained by adding a molybdate dispersion oil containing a lubricating oil and a molybdate to a base grease obtained by incorporating a thickening agent into a base oil, and the molybdate dispersion oil can be obtained by the wet pulverization of the molybdate in the lubricating oil added with a surface active agent. The grease-sealed roller bearing is obtained by sealing at least the circumference of a rolling element 4 with the above grease composition 7.