A guide apparatus including a track rail and a moving block is free from the possibility of foreign matter entering the moving block through the gaps between the side surfaces of the track rail and the inner side surfaces of the moving block even in an environment where many fine dust particles are flying. A guide apparatus has a track rail and a moving block 20 relatively movably attached to the track rail with rolling elements interposed therebetween. The rolling elements recirculate through rolling element recirculation passages. Foreign matter entry preventing plates 34 are provided so that their respective distal ends longitudinally contact the opposite side surfaces of the track rail to close the gaps between the side surfaces of the track rail and at least the inner side surfaces of skirt portions on both sides of a moving block body 21 and the inner side surfaces of end plates of the moving block 20.