To provide a continuous soil conditioning, mixing, agitating, and feeding device capable of efficiently improving soil produced by general constructions which has been difficult to conduct with a conventional pipeline-system mixing and agitating machine and also capable of reducing maintenance work.

This device comprises a hopper 6 capable of regulating a soil supply amount by rotatingly controlling a soil supply amount control screw 8 at a soil inlet side and a mixing and agitating device having a separate driving device. By controlling their rotations separately, a supplied amount, a mixing and agitating time, and a discharged production amount can be controlled.