The inner elastic sealing member 5 includes an inner cylindrical base portion 5A leading to an end portion of an inner cylindrical portion 1B of the inner ring 1, and also includes, at an outer circumferential surface of the inner cylindrical base portion 5A, a projection 7 extending radially outward of an inner periphery of a lower end of an inner cylindrical portion 2B of the outer ring 2. The outer elastic sealing member 6 includes a lip 6B brought into pressure contact with a pressure contact surface B of the outer ring 2. An upper surface 7A of the projection 7 is spaced downward from the lower end of the inner cylindrical portion 2B of the outer ring 2, and an outer circumferential surface 7C of the projection 7 is spaced radially inward from the lower member 8.