To provide an installation structure for a screw element capable of installing the screw element to a desired position along a continuous opening formed in a member such as a support by extremely simple work using a simple structure.

The continuous opening 332 comprises of a plurality of small grooves 334a and 334b continuously formed to operate as screw grooves in mutually facing walls 333. The small grooves 334a and 334b provided in one of the mutually facing walls 333 are displaced to the small grooves 334a and 334b provided in the other of the mutually facing walls 333 by a half pitch. By driving the screw element 7 to the small grooves 334a and 334b at a desired position in a length direction of the continuous opening 332, the screw element 7 can be installed onto the continuous opening 332.