The motion guide device includes: a track rail including insertion holes for fixing bolts; and a moving block assembled to the track rail through intermediation of a large number of rolling elements. The moving block includes an adhering matter path provided at a position opposed to the insertion holes of the track rail, the adhering matter path allowing matters adhering on the track rail to pass from one end to another end of the moving block. A pair of path forming members are fixed to both ends of the moving block in a moving direction thereof. The path forming members each include: a pair of end seal portions which traverse rolling-element rolling surfaces of the track rail and abut against a surface of the track rail; and a path opening portion which is provided between the end seal portions and forms an entrance of the adhering matter path.