To provide a branching and joining device, having little weight, not occupying much space and simple in operation, for the rail of a single rail carrier having auxiliary rails at both sides of the main rail.

At the branching part where auxiliary rails are provided at both sides of a main rail 1, the single rail part of the main rail 1 and the starting end of the branching rail are connected by a movable rail (the main rail 1) and a connection 3, a supporting column is provided at the middle part of the movable rail, a rotary connecting plate 14 is provided to the supporting column, the about center parts of the two starting parts of the two branching rails are passed at one side of the auxiliary rails 2a, and a branching device to compose the auxiliary rails 2a and 2b at the inside and the outer side of a branch A21 and a branch B22 symmetrically in the lateral direction respectively is composed. While the inner side auxiliary rail 2b and the outer side auxiliary rail 2a are composed allowable to install as they are, by turning them 180° reversely, the auxiliary rail 2a held by the movable rail is composed in a single line so as to realize a small size.