To provide a method for designing a screw type conveyor having a high conveying efficiency.

The method for designing the conveyor having a screw conveyor for lifting the subject to be conveyed and a pushing screw conveyor for pushing the subject to be conveyed into the lifting conveyor includes determining a necessary pressure curve showing the necessary pressure within a lifting cylindrical casing and a generated pressure curve showing the pressure generated within a pushing cylinder casing, from an equation showing pressure at a certain position of the subject to be conveyed which is packed in the cylindrical casings; then determining, using a discharge efficiency curve, a discharge angle which corresponds to design discharge efficiency; determining the pressure needed for lifting, based on the necessary pressure curve which matches the discharge angle; generating the generated pressure equal to or greater than the required pressure in the pushing conveyor; and determining the rotation speed of the screw of each of the lifting and pushing conveyors based on the discharge efficiency, design discharge efficiency, and design amount of conveyance of the pushing conveyor matched the generated pressure.