To provide a connection structure of a cross rail, which does not newly require bolts, metal fittings or the like for exclusive use even if bolt-holes need to be formed in the cross rail on the spot when a connection member is connected with the cross rail for use in a fence or the like, thereby restraining the degradation of its construction performance and the increase in component cost.

The cross rail 2 is attached via bolts 4 to a connection member 3 attached to a post 1. In either end of the cross rail 2, a bolt through-hole 21 is formed through which the bolt 4 penetrates. The bolt through-hole 21 on one side is long hole-shaped, and the bolt through-hole 21 on the other side is circular hole-shaped. The bolt 4 is of the type of a cup square neck bolt. A square neck formed on an undersurface of the head part can be fitted into the long hole-shaped through-hole, and can not be fitted into circular hole-shaped through-hole. On the top surface of the head part of the bolt 4, a polygon-shaped engagement hole is formed into which a polygon-shaped wrench is fitted.