To solve the problem that a screw thread can destroy the wall face or the like made of a brittle material and a screw is idly turned by a rotating torque caused at the time of pressing a metal fitting of a building with a head of the screw if the metal fitting part is tightened by rotating the screw.

When the shortest distance from the center of a screw hole to the edge of the metal fitting is set to L1 and the thickness of the metal fitting to T1, the smaller penetration hole than a screw thread diameter which is made of a metal plate with an optionally-shaped outside diameter and the platy hollow part are prepared. The fixing unit consisting of a screw fixing auxiliary device 1 with the hanging down projection in the same direction as a pan-like hollow part and a screw body into a penetration hole are obtained on the outer circumference of the metal plate which the distance L2 from the center of the penetration hole in the distance exceeds L1.