A exhaust cooling system for an internal combustion engine, the exhaust cooling system comprising: an exhaust purification catalyst arranged in an exhaust passage of the internal combustion engine; a cooling unit configured to cool the exhaust passage upstream of the exhaust purification catalyst; a curved section positioned in the exhaust passage downstream from a location cooled by the cooling unit to the exhaust purification catalyst, the curved section including an inner curved section with a relatively small curvature radius and an outer curved section with a relatively large curvature radius in a cross section including a central axis in a longitudinal direction of the exhaust passage; a heat radiation suppression portion (12a, 12b, 13a, 13b) provided at the inner curved section and the outer curved section in the curved section, characterized in that the heat radiation suppression portion (12a, 12b, 13a, 13b) is configured to suppress heat radiation transmitted from exhaust gas flowing in the curved section to an atmosphere around the curved section through curved section passage walls forming the curved section, wherein a heat radiation suppression capacity of the heat radiation suppression portion (12a, 12b, 13a, 13b) in the inner curved section is higher than a heat radiation suppression capacity of the heat radiation suppression portion (12a, 12b, 13a, 13b) in the outer curved section, the heat radiation suppression portion (12a, 12b, 13a, 13b) is configured as a hollow multiwall tubular structure in which an inner tube and an outer tube are arranged apart from each other in a predetermined heat radiation suppression region including the curved section in the exhaust passage; and a first exhaust passage located downstream of the cooling unit and upstream of the predetermined heat radiation suppression region is configured as a multiwall tubular structure with the number of tubes less than that in the predetermined heat radiation suppression region. an exhaust purification catalyst arranged in an exhaust passage of the internal combustion engine; a cooling unit configured to cool the exhaust passage upstream of the exhaust purification catalyst; a curved section positioned in the exhaust passage downstream from a location cooled by the cooling unit to the exhaust purification catalyst, the curved section including an inner curved section with a relatively small curvature radius and an outer curved section with a relatively large curvature radius in a cross section including a central axis in a longitudinal direction of the exhaust passage; a heat radiation suppression portion (12a, 12b, 13a, 13b) provided at the inner curved section and the outer curved section in the curved section, characterized in that the heat radiation suppression portion (12a, 12b, 13a, 13b) is configured to suppress heat radiation transmitted from exhaust gas flowing in the curved section to an atmosphere around the curved section through curved section passage walls forming the curved section, wherein a heat radiation suppression capacity of the heat radiation suppression portion (12a, 12b, 13a, 13b) in the inner curved section is higher than a heat radiation suppression capacity of the heat radiation suppression portion (12a, 12b, 13a, 13b) in the outer curved section, the heat radiation suppression portion (12a, 12b, 13a, 13b) is configured as a hollow multiwall tubular structure in which an inner tube and an outer tube are arranged apart from each other in a predetermined heat radiation suppression region including the curved section in the exhaust passage; and a first exhaust passage located downstream of the cooling unit and upstream of the predetermined heat radiation suppression region is configured as a multiwall tubular structure with the number of tubes less than that in the predetermined heat radiation suppression region.