A ball bearing comprising: an outer ring having an inner periphery raceway groove; an inner ring having an outer periphery raceway groove and a ring-shaped member fitted portion (22, 23) that has a step portion (51, 52) that extends generally along a radial direction of the outer ring and an outer peripheral face portion; balls disposed between the inner periphery raceway groove of the outer ring and the outer periphery raceway groove of the inner ring; a ring-shaped lubricant supply member (4, 5) that is fixed to the ring-shaped member fitted portion (22, 23) while being in contact with the step portion (51, 52), wherein the ring-shaped member fitted portion (22, 23) is an annular groove (22, 23) that is located in an outer periphery of the inner ring; and the lubricant supply member (4, 5) is fixedly fitted in the annular groove (22, 23); and a shield plate (7, 8) that is fixed to the outer ring, that is located with a clearance left between the shield plate (7, 8) and the outer periphery of the inner ring, and that overlaps with the lubricant supply member (4, 5) in a radial direction of the inner ring, wherein when a maximum outside diameter of a portion of the outer periphery of the inner ring, the portion being located on an opposite side of the annular groove (22, 23) from the outer periphery raceway groove in an axial direction of the inner ring, is Di, an inside diameter of the lubricant supply member (4, 5) is dL, an inside diameter of the shield plate (7, 8) is dZ, an elastic deformation limit of the lubricant supply member (4, 5)in the radial direction is δL, and an outside diameter of the lubricant supply member (4, 5) is DL, Di < dL + δL and DL < dZ are satisfied. an outer ring having an inner periphery raceway groove; an inner ring having an outer periphery raceway groove and a ring-shaped member fitted portion (22, 23) that has a step portion (51, 52) that extends generally along a radial direction of the outer ring and an outer peripheral face portion; balls disposed between the inner periphery raceway groove of the outer ring and the outer periphery raceway groove of the inner ring; a ring-shaped lubricant supply member (4, 5) that is fixed to the ring-shaped member fitted portion (22, 23) while being in contact with the step portion (51, 52), wherein the ring-shaped member fitted portion (22, 23) is an annular groove (22, 23) that is located in an outer periphery of the inner ring; and the lubricant supply member (4, 5) is fixedly fitted in the annular groove (22, 23); and a shield plate (7, 8) that is fixed to the outer ring, that is located with a clearance left between the shield plate (7, 8) and the outer periphery of the inner ring, and that overlaps with the lubricant supply member (4, 5) in a radial direction of the inner ring, wherein when a maximum outside diameter of a portion of the outer periphery of the inner ring, the portion being located on an opposite side of the annular groove (22, 23) from the outer periphery raceway groove in an axial direction of the inner ring, is Di, an inside diameter of the lubricant supply member (4, 5) is dL, an inside diameter of the shield plate (7, 8) is dZ, an elastic deformation limit of the lubricant supply member (4, 5)in the radial direction is δL, and an outside diameter of the lubricant supply member (4, 5) is DL, Di < dL + δL and DL < dZ are satisfied.