PURPOSE: To facilitate application of a frame to form respective steps of a stepwise slab and spare laborers in maintenance and finishing work after concrete work.

CONSTITUTION: A plurality of support beams 11 are constructed along the diagonal direction at the upper side of the lower face frame 20. A plurality of rise frames 14 are horizontally attached so as to cross in nearly right angles with respective support beams 11 with every specified interval in the lower part of the support beams 11. The level at both ends of the support beam 11 is adjusted by jacking members 16, 17, then, concrete is placed onto the lower face frame 20 and dammed up stepwise by the respective rise frames 14.