To support a wiring box 1 in an excellent state by surely regulating the movement of the wiring box 1.

The wiring box 1 is provided with respective inserting parts 3 each having a through-hole 4 formed in a reverse wall 2 and a swelling part 5 facing the through-hole 4 and projecting from the reverse wall 2 by cutting and raising the reverse wall 2 of its wiring box 1. The wiring box 1 has a movement regulating means M for abutting by being hooked so as to regulate the wiring box 1 from moving in the axis 10a direction of a support bar 10 to the support bar 10, and has a rotational movement regulating means R for abutting by being hooked so as to regulate the wiring box 1 from rotating around the axis 10a of a support bar 10 to the support bar 10, in a support state of inserting both support bars 10 into a support hole 6 formed inside the swelling part 5 of the respective inserting parts 3. The wiring box 1 is supported by installing both ends of both support bars 10 to a reinforcement forming the support rib of a concrete structure.