PURPOSE: To simplify the inside work in the shell of a screw pump and as well to make the screw pump lightweight, thereby it is possible to aim at miniaturizing the shafts and bearings thereof, by forming a longitudinal space coaxial with the axis of a flight between both bearings at the upper and lower end parts of the flight.

CONSTITUTION: A flight 2 is formed therein with a logitudinal space coaxial with the axis of the flight 2 between pump shafts 3, 4. Thereby, the inside work such as, for example, welding of the outer peripheral edge of the flight 2 to the inner peripheral surface of a shell 1 or painting, may be simply made. Further, if a belt-like member adheres to the flight 2, this may be easily removed off. Furhter the flight is secured to the inner peripheral surface of the shell 1 while the pump shafts 3, 4 are secured to parts of the flight 2. Accordingly, the plate thickness of the remaining part of the flight 2 to which neither shafts 3, 4 are secured may be made thin. With this arrangement, the flight may be made from, for example, reinforced plastic so that the flight may be made lightweight, thereby, the pump shafts 3, 4 and bearings 5, 7 may be miniaturized.