To manufacture a cross wall with high degree of accuracy by turning a pivoting jig to make a second pattern face as a horizontal state to form a second wall after a first wall is molded by filling a first pattern face formed in a horizontal state with a molding material by using the pivoting jig having the first and second pattern faces.

A basic frame 4 having the inside formed in an L-shape at right angles and having the outside corner section forming a semi-circular rolling surface projected to the outside is provided close to both ends of a jig 1, and an L-shaped auxiliary frame 12 is provided to the intermediate section. A floor form 2 is provided to one side on the inside corner side of the jig 1, a side wall form 3 is provided to the other side at a certain interval (d) between the side wall form 3 and basic frame 4, the outside end section 3a is pivoted to a contact section 11b of the basic frame 4 in a turnable manner, and the outside wall form 3 is capable of pivoting the inside corner section 3b intersecting the floor form 2 within the interval (d). The floor form 2 of the jig 1 is leveled to fill the floor form with concrete 26, and after the solidification, the jig 1 is inverted, the side wall form 3 is leveled to fill it with the concrete 26 to solidify, and after the drying, stripping is made. By using the pivoting jig 1, work efficiency in the filling of the molding material is improved, and accuracy of products is promoted.