A motion device includes a track rail, a moving body, rolling elements, fixing members each fixed to an end surface of the moving body, and rolling element circulation members arranged between the moving body and the fixing members. The rolling element circulation members each have a connection section connected to the moving body so as to be rotatable about a Y direction, and a pair of first outside surfaces. The fixing members each have accommodation sections to accommodate the rolling element circulation members, and a pair of first inside surfaces closely contact with the pair of first outside surfaces. The respective rolling element circulation members and the accommodation sections are provided at both sides of the track rail interposed there between.