The intake side suction port of the screw type must be designed so that the compression chamber can intake sufficiently. However, screw compressors do not have intake or exhaust valve assemblies; instead, intake is regulated solely by the opening and closing of an adjustment valve. When the rotor rotates, the space between the main and auxiliary rotor grooves reaches its maximum when it turns to the intake end wall opening. At this point, the space in the rotor grooves communicates with the free air at the intake port. Since all the air in the grooves has been fully discharged during the exhaust phase, the grooves are in a vacuum state at the end of the exhaust process. When the rotors turn to the intake port, outside air is sucked in and flows axially into the grooves of the main and auxiliary rotors.