PURPOSE: To improve the performance of a screw compressor, by eliminating leakage of fluid at the region near the discharge opening of the compressor through employment of such an arrangement that rotor shafts are positioned with some displacement toward the discharge side from the axes of a rotor chamber.

CONSTITUTION: Rotor shafts 6a, 6b of a female and a male rotors 5a, 5b are positioned such that the distance between them is kept constant but they are displaced slightly downward from the axes 7a, 7b of a rotor chamber 2 while keeping parallelism with the axes 7a, 7b. In operation, fluid handled by the compressor causes elastic deformation of the rotor shafts 6a, 6b in a direction away from a discharge opening 4. However, since arrangement is such that the rotor shafts 6a, 6b are positioned with some displacement toward the discharge opening 4, gaps 10a, 10b between the rotors 5a, 5b and the inner surface of the rotor chamber 2 at the region near the discharge opening 4 can be kept small, so that leakage of fluid can be prevented.