To produce a concrete member of complex, various shapes economically by immersing a bag-shaped material having an opening in liquid, placing concrete from the opening, and packing the material against a liquid pressure.

It is a placing bath 1, and a bentonite solution 3 is stored in a storage tank 2 formed by concrete. Next, as a form to a prescribed hexahedron shape in advance when filled up, a bag-shaped material 4 of polypropylene is prepared and set in the tank 1 in a folded form, and the opening is left above the level of the bentonite solution 3. Besides, a pipe-shaped introduction part is installed extendingly in one apex part of a hexahedron, and an opening is formed at its end. After that, raw concrete 5 is placed from the opening of the bag-shaped material 4, and the raw concrete 5 is packed in the whole form consisting of the bag-shaped material 4. In this operation, since the density of the concrete 5 is near that of the bentonite solution 3, a small side pressure of its difference is added to the form 4 to make a shape 6A of a prescribed hexahedron.