In a linear guide bearing apparatus wherein a separator is interposed between adjacent balls K and K moving following a curved circulating path 8, and the ball K contacts concave faces W of the separator Tat both ends in an axial line direction and at the same time the ball K rolls as contacting a guide face 8a of an outside guiding member 5 and a guide face 8b of an inside guiding member 9, the separator has an outer diameter larger than a maximum outer diameter L under a condition where the ball rolls as simultaneously contacting both curved faces 8a, 8b of the inside and the outside of the curved circulating path 8, and the radius of curvature of the guiding face 8b in the curved circulating path 8 is reduced to a size not contacting the separator T.