To prevent an upper sliding surface of a rail part from being wavy by providing the rail part comprising a plurality of rail plates which are continuously arranged in the rail width direction, and longitudinally arranged in a row adjacent to the longitudinal direction.

A rail part 3 is formed of a plurality of rectangular rail plates of the same shape, and the rail plates are formed of synthetic resin. In the rail part 3, three rail plates 4A, 4B, 4C are held in parallel in the rail width direction between erected members 2A. Rail plates 5A, 5B, 5C are arranged continuous thereto, and rail plates 6A, 6B, 6C are formed adjacent thereto in the longitudinal direction of the rail, and each rail plate is arranged longitudinally in a row between erected members. Gaps A, B, C are provided between end parts of the rail plates which are longitudinally arranged adjacent to each other, the gaps are arranged straight in the rail width direction, and the continuously arranged rail plates 4A, 4B, 4C are not deviated in position from each other.