PURPOSE: To prevent water, foreign objects and the like from coming into bearings from outside by forming a self-tension type sealing body which combines each sliding body with each elastic body pressing said sliding body, between the both end sections of the bearings in double rows and between mutual rolling elements at the center section.

CONSTITUTION: Each rubber elastic body 19 is incorporated into a self-tension type sealing body insertion chamber while being imparted with some contraction margin so that it acts in a state that each sliding body 20 is pressed onto a set of bearing outer race spacers, lubricant injected in advance into each space section within rolling elements 14 in bearings will never come outside through self-tension type bodies 19 and 20. When lubricant is fed into a mating surface between a bearing inner shaft 13 and a roll neck 1 from the A direction, lubricant flows in the mating surface of the roll neck 1 through the passage port within the spacer 18 and each passage port of the contact sections of inner races 13a and 13b so as to be pressurized because the clearance gap of the mating surface is small. In this case, the elastic body 19 furthermore presses the sliding body 20 against the sliding surface of the spacer 19, lubricant thereby will never flow in the bearings from sealing surfaces.