A rotor profile for screw compressors is disclosed. The rotor profile is shown in a latitudinal cross-section taken along a line extending in a direction perpendicular to rotor axes, and is applied to male and female rotors used in a screw compressor having a housing defining an actuating space therein, the male rotor being rotatably set in the actuating space and having spiral teeth and roots defined between the teeth, and the female rotor being set in the actuating space to rotatably engage with the male rotor and having spiral teeth and roots defined between the teeth. The rotor profile comprises a first curve F-G determined as a circular arc and inscribed in an addendum circle of the female rotor at a point “G” around a trailing end of each tooth of the female rotor, and a second curve determined by a hyperbola function r=(&egr;·K)/(1−&egr;·cos &thgr;), wherein 1.1≦&egr;≦1.15, and a derived function of first order of the hyperbola function of the second curve at a point “F” is equal to a derived function of first order of a function of the curve F-G. Due to the curve E-F, the blow-hole size is preferably minimized while the pressure angle of a rotor machining tool is maintained at a level of at least 8°. In addition, due to an appropriately limited wrap angle of the male rotor, the pressure angle of the rotor machining tool is increased and desired tooth strength is maintained.