A turbocharger comprising: a compressor housing having internally an air flow path in which an impeller is arranged, and a bearing housing rotatably supporting a rotor shaft on one end of which the impeller is fixed, wherein the air flow path has an air intake port for sucking air toward the impeller and a discharge scroll chamber formed in the circumferential direction on the outer circumferential side of the impeller to guide compressed air discharged from the impeller to the outside; the compressor housing has a shroud surface opposite to the impeller and a diffuser surface extending from the shroud surface toward the discharge scroll chamber; the bearing housing has an opposite surface facing the diffuser surface of the compressor housing to form a diffuser passage between the opposite surface and the diffuser surface; an adhesion preventing part for preventing the adhesion of a deposit is provided on at least one of the diffuser surface of the compressor housing and the opposite surface of the bearing housing; the adhesion preventing part has a surface forming part having many fine through holes which open to the side of the diffuser passage and an air tank part covered with the surface forming part from the side of the diffuser passage and configured so as to be in communication with the air flow path on the downstream side of the diffuser passage so that a part of compressed air is supplied; the turbocharger is configured so that compressed air supplied to the air tank part spouts out to the diffuser passage through the through holes by an ejector effect caused when compressed air passes through the diffuser passage; characterised in that the through holes are formed along a virtual curve in the diffuser passage, the virtual curve being curved in such a manner that the closer the curve comes to the downstream side of the diffuser passage from a starting point, the more distant the curve is in a direction opposite to a rotating direction of the impeller, with respect to such a virtual straight line passing the starting point that an angle formed with a tangent line at the outer edge of the impeller from the starting point coincides with a backward angle (α) of the impeller. a compressor housing having internally an air flow path in which an impeller is arranged, and a bearing housing rotatably supporting a rotor shaft on one end of which the impeller is fixed, wherein the air flow path has an air intake port for sucking air toward the impeller and a discharge scroll chamber formed in the circumferential direction on the outer circumferential side of the impeller to guide compressed air discharged from the impeller to the outside; the compressor housing has a shroud surface opposite to the impeller and a diffuser surface extending from the shroud surface toward the discharge scroll chamber; the bearing housing has an opposite surface facing the diffuser surface of the compressor housing to form a diffuser passage between the opposite surface and the diffuser surface; an adhesion preventing part for preventing the adhesion of a deposit is provided on at least one of the diffuser surface of the compressor housing and the opposite surface of the bearing housing; the adhesion preventing part has a surface forming part having many fine through holes which open to the side of the diffuser passage and an air tank part covered with the surface forming part from the side of the diffuser passage and configured so as to be in communication with the air flow path on the downstream side of the diffuser passage so that a part of compressed air is supplied; the turbocharger is configured so that compressed air supplied to the air tank part spouts out to the diffuser passage through the through holes by an ejector effect caused when compressed air passes through the diffuser passage; characterised in that the through holes are formed along a virtual curve in the diffuser passage, the virtual curve being curved in such a manner that the closer the curve comes to the downstream side of the diffuser passage from a starting point, the more distant the curve is in a direction opposite to a rotating direction of the impeller, with respect to such a virtual straight line passing the starting point that an angle formed with a tangent line at the outer edge of the impeller from the starting point coincides with a backward angle (α) of the impeller.