To perform separation of materials and reduce the cost of transportation.

A chute placement device 12 has a cylindrical drum 12a, a spiral vane 12b having an outer periphery edge fixed into the drum 12a and a rotation driving mechanism 12c for the drum 12a. The drum 12a is extended along a slope 20 from around a concrete plant 10 to a placement position at the lower end of the slope 20, with its opening at the upper end being communicated with a material supply part 14, and rotatably supported via a bearing part 12d. The spiral vane 12b is provided throughout the total length of the drum 12a, with its spiral space 24 along the slope 20 being formed in the drum 12a in isolated relation by the drum 12a and the spiral vane 12b. A concrete structural material is charged from the upper end of the spiral space 24, the charged concrete structural material is kneaded with flow-down while rotating the spiral space 24 and the kneaded concrete structural material is received at the lower end in the spiral space 24.