A motion guide device (1) includes: a track body that extends in a longitudinal direction; a movable body (20) that is mounted on the track body and is movable along the track body; an encoder scale that is disposed at the track body in the longitudinal direction; a sensor (50) that is disposed opposite to the encoder scale; and a folder (60) that is disposed at an end face of the movable body (20) in the longitudinal direction, houses the sensor (50) in a width direction of the track body, and holds the sensor such that the sensor faces the encoder scale.