PURPOSE: To facilitate the manufacture of a form and omit mortar finishing so as to shorten a construction period and to reduce the construction cost.

CONSTITUTION: The fixing plates 7 of adjusting fittings 3 are nailed to points on a floor form 4 to assemble a riser 1, and the support reinforcing bars 2b of tension fittings 2 are fixed to the floor form 4 to support the upper part of the riser 1, thus forming a stair form 9. Concrete 11 is then placed into the stair form 9 from the tread part to embed the riser 1, thus constructing a stairway.