A motion guide apparatus which prevents a retainer from falling-off. A motion guide apparatus includes a track member having a rolling element rolling portion; a movable member having a loaded rolling element rolling portion facing the rolling element rolling portion of the track member; a return path; and a turn-around path connected to a loaded path and the return path; a plurality of rolling elements placed in the loaded path, the return path, and the turn-around path; and a retainer configured to hold at least one of the plurality of rolling elements. Grooves into which an end of the retainer in a width direction thereof enters are formed in the loaded path, the return path, and the turn-around path. A width of the grooves in at least a part of the turn-around path and/or in the return path is greater than a width of the groove in the loaded path.