PURPOSE: To shorten the period of construction by quickly performing the placement of concrete and the water-proofing treatment of outer walls by using a formwork unit consisting of a base plate, metal tools for fitting iron bars, plural nuts, and iron bars fitted in a latticed form.

CONSTITUTION: A mould unit 11 consists of a base plate 12 of steel plate, corrugated iron bars-fitting metal tools 13 welded to one side of the base plate 12, plural nuts 14 welded to the base plate 12, iron bars 16 attached in a latticed form to the metal tools 13 by wires 15, and a grooved body 17 fixed to the edge of the base plate 12. Struts 22 are provided to a concrete mat 21, and the mould unit 11 is fixed with bolts between the struts 22. Inner iron bars 23 are set to construct an inside mould 24, the outside and inside moulds 11 and 24 are held at a given interval by a separator 25, and concrete 28 is placed to complete the outer wall on the lowest stage.