To improve external apperance and safety of a frame body by V cut bending of a member by bending it by butting a V-shaped notch part against a member having a V-shaped notch part in an intermediate part, and installing a cover to hide a butting part in a bending part.

After a section 2 on which work of a V-shaped notch part 4 and a notch hole 5 is completed is bent until the cutting edge of the notch part 4 is butted in a close contact condition, a cover 3 is put on an inner peripheral part of a bending part, and a engaging projection 3d of the cover 3 is locked on the notch hole 5 of the section 2. Since a locking piece of the cover 3 is inserted into an opening part 2d of the section 2 and is firmly fitted between projecting pieces 2c, an installing condition of the cover 3 is stabilized. The projecting pieces 2c of the section 2 are sandwiched between a side piece and the locking piece of the cover 3, and a step difference is not caused in a butting part. Since the cover 3 hides the notch edge of the section 2, even if dislocation is caused when it is used, it cannot be seen from outside.