PURPOSE: To ensure spares on the sides of rails even when empty regions, the openings of joints, are left inevitably.

CONSTITUTION: A rail coupling device for coupling rails laid on frames, particularly the trusses of a bridge with a foundation 5 or rails extended on a ground surface has expansion points 3, and expansion openings are bridged by cross arms or beams 6, 8 elongated in the lateral direction to the longitudinal direction of the rails in regions among the end-section trusses 2 and the foundation 5. The cross arms or the beams 6, 8 are supported slidably to parts of the trusses or the end sections of the foundation 5, and the rails are supported to the cross arms or the beams 6, 8.