To provide a thin-walled double-row ball bearing wherein a predetermined amount of grease is sealed therein, while preventing initial leakage of grease, even though the bearing is of the thin-walled type with a small bearing cross-sectional width as balls with a small diameter are used.

In the double-row ball bearing 1 with a bearing cross-sectional width of 7.5 mm or less and a ball diameter of 4 mm or less, a grease filler port 15 is formed between the double rows of raceway grooves 2 and 3 of an outer ring 4. To inject grease a nozzle 17 of a grease injector 16 is inserted into the grease filler port 15 to inject a predetermined amount of grease into a bearing internal space 18. Because the grease filler port 15 is closed by the inner surface of a pulley or the like upon the assembly of the bearing into a compressor pulley or the like, the grease therein will not leak out. The grease filler port may be provided in an inner ring 7 or may be formed as a grease filling groove on the inner peripheral surface of the outer ring while facing an axial end face of the bearing from either of the rolling grooves of the outer ring 4.