The object is to provide a compressor housing which can suppress blowback of oil. A compressor housing (1) is used in a compressor which uses a compressor impeller (5) provided in an intake air flow path more to a downstream side than a blow-by gas inlet. The compressor housing (1) includes an impeller chamber (2), and an intake air duct (6) which extends along an axis line (C). The duct (6) includes an inner-wall face (61). A step part (67) that is arc shaped along a circumferential direction of the impeller (5) and has a distance along the radial direction of the impeller (5) from the axis line (C) that is farther at a downstream side than at an upstream side thereof is formed in the inner-wall face (61) more to an upstream side along the axis line (C) than the intake air inlet (22).