To solve problems that a joint and bracket and a rectilinearity holding spring are required to be provided projectedly in a front wall in a conventional device, and a folding effect of a traction bar is not obtained thereby, and that structure is not only complicated but also strength and durability are required to be improved, since angle displacement of the traction bar is operated via a large number of steering transmission members interlocked in accopaniment to rotation of an angle displacing shaft erected in a retrieval bar.

In this steering device for a full-trailer wherein a front steering shaft type trailer mounted with a steering shaft mechanism 101 in its front part is towed by a tractor using the traction bar, a horizontal rotary bearing part 104 rotating lateral-directionally around a connection shaft 102 as the center provided in the full-trailer is provided in the traction bar 103, and the steering transmission members 105, 110, 113, 115 are interlocked with the horizontal rotary bearing part to steer the steering shaft mechanism.