To provide a soil improvement machine capable of surely sending earth and sand thrown in a hopper to a transport device.

Through-holes 25C, 26C and 27C are made in the left circumferential surface 25, the right circumferential surface 26 and the front circumferential surface 27 of the hopper 24, the insides of the circumferential surfaces 25, 26 and 27 are covered with the left flexible sheet 29, the right flexible sheet 31 and the front flexible sheet 33, pressure cylinders 35 pressing the flexible sheets 29, 31 and 33 are provided to the outside of the circumferential wall surfaces 25, 26 and 27 through the through-holes 25C, 26C and 27C. Even if earth and sand A thereby adhere to the upper surfaces of the flexible sheets 29, 31 and 33, rods 35B of the pressure cylinders 35 pressure the flexible sheets 29, 31 and 33 through the through-holes 25C, 26C and 27C to deform the flexible sheets 29, 31 and 33, and the earth and sand A adhering to the upper surface thereof are separated to surely send the earth and sand to the transport conveyor 8.