A separator for use in a linear guide apparatus including a guide rail, a slider, and a plurality of rollers which circulate along an endless circulation passage provided in the guide rail and the slider and having guide grooves. The separator includes a separator body interposed between the rollers and having a pair of roller contact surfaces respectively opposing outer peripheral surfaces of the adjacent rollers, and a pair of arm portions which are guided by the guide grooves. A surface of each of the arm portions opposing the guide groove is formed such that an opposition distance with respect to the guide groove becomes wider from a fixed end side of the arm portion toward a free end thereof.