A screw pump includes a pair of screw rotors (2a, 2b) having teeth which are held in mesh with each other for drawing and discharging a fluid by rotating the screw rotors (2a, 2b) synchronously in opposite directions. The teeth of the screw rotors (2a, 2b) have the same shape as each other and are coiled helically in opposite directions. The teeth of the screw rotors (2a, 2b) have an axial tooth profile which allows a pair of facing teeth surfaces T of the screw rotors (2a, 2b) to be brought into contact with each other only at a pitch line P when the pair of facing teeth surfaces T are brought into contact with each other.