A screw compressor includes: a male rotor 2 and a female rotor 3 including a rotor tooth section 21, 31 that has multiple helical teeth, the male rotor 2 and the female rotor 3 rotating in engagement with each other; a casing 4 including a main casing 41 with a bore 45 formed to accommodate the male rotor 2 and the female rotor 3, and a discharge-side casing 43 closing a discharge side of the bore 45; and a discharge passage 60 including a discharge port 61 that opens in a rotational axis direction of the male rotor 2 and the female rotor 3 on a bore side surface of the discharge-side casing 43, compressed gas flowing from the discharge port 61 circulating in the discharge passage 60. The male rotor 2 and the female rotor 3 are configured such that a discharge-side end surface 21a, 31a of the rotor tooth section 21, 31 serves as a discharge-side distal end of the male rotor 2 or the female rotor 3 in the rotational axis direction. The discharge passage 60 includes an enlarged flow passage section 63 formed such that the enlarged flow passage section 63 extends from the discharge port 61 in the rotational axis direction of the male rotor 2 and the female rotor 3 and that a flow passage cross-sectional area is gradually enlarged from the discharge port 61 to a downstream side in a compressed gas flow direction.