To heighten a withstand load when a moment load is applied and reduce the generation of backlash by accommodating a pair of slide bearings with a linear ball bearing interposed between them at both ends in a housing, and setting the inside diameter of each slide bearing larger than the outline of a shaft inserted in the bearing.

Linear ball bearings 10, 10 and slide bearings 20, 20 are disposed such that a pair of linear ball bearings are interposed between a pair of slide bearings, and with an oiling member 30 interposed between the linear ball bearings, they are inserted in a housing 1. The oiling member 30 disposed between the respective linear ball bearings 10, 10 is shaped like a ring which can be inserted in the housing 1, and provided with an annular oil groove 32 disposed in the outer periphery, and with an annular oil groove 31 surrounding the outer periphery of the shaft of the bearing, both grooves being communicated with each other by an oil hole 33. The inside diameter of each slide bearing 20, 20 is set larger than the outside diameter of the shaft inserted in the bearing.