An axial-flow turbine which is driven by exhaust gas discharged from an internal combustion engine, the turbine comprising: a turbine rotor blade; an exhaust gas inlet casing that forms an inner periphery side flow path of the exhaust gas, introducing the exhaust gas that flows in through an exhaust gas inlet in a direction intersecting a rotary shaft direction of the turbine rotor blade, to the turbine rotor blade; characterised by an exhaust gas guide section for introducing exhaust gas which has passed through the axial-flow turbine to an exhaust gas outlet of an exhaust outlet casing bonded to the exhaust gas inlet casing; a bypass section that is provided in an outer periphery of the exhaust gas inlet casing and forms a bypass flow path for introducing the exhaust gas to the exhaust gas outlet without causing the exhaust gas to pass through the turbine rotor blade; and an opening/closing valve that performs opening and closing of the bypass flow path, wherein the exhaust gas inlet casing includes a first opening section which communicates with an inlet section of the bypass flow path, and a second opening section which communicates with an outlet section of the bypass flow path, wherein the second opening section communicates with an outer periphery side flow path for introducing the exhaust gas to the exhaust gas guide section, thereby being discharged to the outside through the exhaust gas outlet of the exhaust outlet casing together with exhaust gas which has passed through the turbine rotor blades, wherein the outer periphery side flow path is arranged closer to an outer periphery side of the axial-flow turbine than the inner periphery side flow path; and the bypass section is a pipe member which is fixed to the first opening section and the second opening section. a turbine rotor blade; an exhaust gas inlet casing that forms an inner periphery side flow path of the exhaust gas, introducing the exhaust gas that flows in through an exhaust gas inlet in a direction intersecting a rotary shaft direction of the turbine rotor blade, to the turbine rotor blade; characterised by an exhaust gas guide section for introducing exhaust gas which has passed through the axial-flow turbine to an exhaust gas outlet of an exhaust outlet casing bonded to the exhaust gas inlet casing; a bypass section that is provided in an outer periphery of the exhaust gas inlet casing and forms a bypass flow path for introducing the exhaust gas to the exhaust gas outlet without causing the exhaust gas to pass through the turbine rotor blade; and an opening/closing valve that performs opening and closing of the bypass flow path, wherein the exhaust gas inlet casing includes a first opening section which communicates with an inlet section of the bypass flow path, and a second opening section which communicates with an outlet section of the bypass flow path, wherein the second opening section communicates with an outer periphery side flow path for introducing the exhaust gas to the exhaust gas guide section, thereby being discharged to the outside through the exhaust gas outlet of the exhaust outlet casing together with exhaust gas which has passed through the turbine rotor blades, wherein the outer periphery side flow path is arranged closer to an outer periphery side of the axial-flow turbine than the inner periphery side flow path; and the bypass section is a pipe member which is fixed to the first opening section and the second opening section.