A turbine housing , comprising: an inlet-side casing including a scroll portion having therein a scroll passage ; an outlet-side casing fastened to the inlet-side casing by a first fastening member ; and a passage forming member including a passage wall surface that defines an exhaust gas passage for guiding an exhaust gas from the scroll passage to a turbine wheel , wherein the outlet-side casing includes: a cylindrical portion having therein an outlet passage through which the exhaust gas having being guided from the scroll passage to the turbine wheel and passed through the turbine wheel flows; a flange portion protruding radially outward from a downstream end portion of the cylindrical portion wherein the flange portion is fastened to the scroll portion by the first fastening member , and characterized in that the passage forming member is fastened to the outlet-side casing by a second fastening member ; wherein the outlet-side casing further includes an annular plate portion protruding radially outward from an upstream end portion of the cylindrical portion and fastened to the passage forming member by the second fastening member , wherein the annular plate portion abuts on a back surface of the passage forming member on an opposite side in an axial direction from the passage wall surface ; wherein the annular plate portion has at least one recess that is recessed radially inward from an outer peripheral end of the annular plate portion . an inlet-side casing including a scroll portion having therein a scroll passage ; an outlet-side casing fastened to the inlet-side casing by a first fastening member ; and a passage forming member including a passage wall surface that defines an exhaust gas passage for guiding an exhaust gas from the scroll passage to a turbine wheel , wherein the outlet-side casing includes: a cylindrical portion having therein an outlet passage through which the exhaust gas having being guided from the scroll passage to the turbine wheel and passed through the turbine wheel flows; a flange portion protruding radially outward from a downstream end portion of the cylindrical portion wherein the flange portion is fastened to the scroll portion by the first fastening member , and characterized in that the passage forming member is fastened to the outlet-side casing by a second fastening member ; wherein the outlet-side casing further includes an annular plate portion protruding radially outward from an upstream end portion of the cylindrical portion and fastened to the passage forming member by the second fastening member , wherein the annular plate portion abuts on a back surface of the passage forming member on an opposite side in an axial direction from the passage wall surface ; wherein the annular plate portion has at least one recess that is recessed radially inward from an outer peripheral end of the annular plate portion . a cylindrical portion having therein an outlet passage through which the exhaust gas having being guided from the scroll passage to the turbine wheel and passed through the turbine wheel flows; a flange portion protruding radially outward from a downstream end portion of the cylindrical portion wherein the flange portion is fastened to the scroll portion by the first fastening member , and characterized in that the passage forming member is fastened to the outlet-side casing by a second fastening member ; wherein the outlet-side casing further includes an annular plate portion protruding radially outward from an upstream end portion of the cylindrical portion and fastened to the passage forming member by the second fastening member , wherein the annular plate portion abuts on a back surface of the passage forming member on an opposite side in an axial direction from the passage wall surface ; wherein the annular plate portion has at least one recess that is recessed radially inward from an outer peripheral end of the annular plate portion . <EOS>