There are provided a rail (10) in which a rolling member rolling surface (11) is formed along the longitudinal direction, a block (20) in which a loaded rolling member rolling surface (27) is formed in an opening (25) comprising a through hole, a plurality of balls (70) disposed and housed between the rolling member rolling surface (11) and the loaded rolling member rolling surface (27) which circulate according to the relative motion of the rail (10) and the block (20). A sectional shape at right angles to the longitudinal direction of the rail (10) and a sectional shape of the opening (25) are formed into a mutually geometrically similar longitudinal shape. The block (20) is a box type with high rigidity. A contact angle of the ball (70) can be optionally changed by changing the positions alone of the rolling member rolling surface 11 and the loaded rolling member rolling surface (27) to be machined on one type of the block (20) and the rail (10).