PURPOSE: To provide a temporary building material supporting fitting easy in handling, capable of achieving the work from the indoor side including the removal after a permanent handrail is installed, and excellent in stability and safety.

CONSTITUTION: A first L-shaped member 1 is joined with a second member 2 by bolts 7 while the clearance between an indoor side plate 1b and an outdoor side plate 2b using screw holes ld for adjusting the holding width of the first member 1, and a support member 4 and a temporary handrail supporting member 6 are screwed to the upper surface. An assembled supporting piece S is provided across a balcony riser part of an existing floor, and fixed to the riser part 12 by a tightening piece 3. A single tube 11 for the temporary handrail 11 is externally fitted to a temporary handrail supporting member 6, the temporary handrail and a safety net are fitted thereto, and a pipe support 10 for the execution of upper floors is externally fitted to the support member 4. The supporting piece S is drawn from the clearance below the permanent handrail into the indoor side by loosening tightening bolts 3b and being collapsed in the condition where the support member 4 is removed after the permanent handrail is installed while the temporary handrail is left.