To provide a fixture for forming a hole for embedding a post whose dimension can freely be changed corresponding to thickness of a concrete parapet and to a drainage slope of an upper face of the parapet.

The fixture for forming a hole for embedding a post is composed of a hole-forming body corresponding to a predetermined dimension of the embedding hole, a positioning member mounted on a base end surface of the member, a width-adjusting member corresponding to the thickness of the parapet and a timbering frame for fixing a downstream end of the parapet. The hole-forming body is covered with a resin-made bag while the bag is interposed between the top end of the hole-forming body and the positioning member, so as not to be fallen off. Also, a nut is firmly fixed on the top end of the hole-forming body and the positioning member and the width-adjusting member are fastened by an eye bolt while a retainer is fastened by the eye bolt fixed on the width-adjusting member. Furthermore, fastening holes for the respective bolts are loose holes so that each member can be slidable.