A screw compressor of the present invention comprises: a housing having a compression chamber; male and female rotors provided in the compression chamber; a driving shaft for rotating the male and female rotors; and a seal cover across which the driving shaft is provided^ and further includes: an oil chamber provided at the seal cover^ and returning^ to the compression chamber^ oil having leaked into the driving shaft; and a breather for injecting external air into the oil chamber. Therefore^ the breather is provided at the upper part of the oil chamber and an oil recovery line is provided at the lower part thereof so as to cause a pressure difference between the upper and lower parts of the oil chamber^ such that the flow of the oil having leaked into the driving shaft is smoothly recovered in the oil recovery line.