A motion guide apparatus ensures that a retaining portion retains a rolling element. A rolling element retainer having retaining portions that prevent a rolling element from falling out of a movable body, the retaining portions extending along a loaded rolling element rolling portion, is incorporated in the movable body of the motion guide apparatus. End plates are formed integrally with the retaining portions. Fall prevention portions to reduce the widths of openings between the retaining portions are provided to center parts of the retaining portions in a length direction thereof. The fall prevention portions are padding portions integrated with the retaining portions, the padding portions rising in such a manner as to reduce the widths of the openings, and/or projections integrated with the retaining portions, the projections touching the movable body in such a manner that the center parts of the retaining portions bend toward a track member.