A method for manufacturing an exhaust gas purifying apparatus that includes: a casing; an exhaust gas treating body housed in the casing; and a holding sealing material (10, 10a, 10b) that is wrapped around the exhaust gas treating body and disposed between the exhaust gas treating body and the casing, the method comprising: producing the holding sealing material (10, 10a, 10b) by a method for producing a holding sealing material (10, 10a, 10b) comprising: a material mat preparing step of preparing a material mat (100, 110) that comprises inorganic fibers and has a mat shape with a first main face (101, 111), a second main face (102, 112) opposite to the first main face, side faces along a longitudinal direction of the material mat, and end faces along a width direction perpendicular to the longitudinal direction; and a deformation step of plastically deforming the material mat (100, 110) by immobilizing the first main face (101, 111) and the second main face (102, 112) of the material mat, and applying a shear stress to the first main face (101, 111) and the second main face (102, 112) respectively in mutually opposite directions along the width direction, wherein the material mat (100, 110) prepared in the material mat preparing step is a material mat impregnated with an organic binder solution, and in the deformation step, the material mat (100, 110) is immobilized and dried while the shear stress is applied to the first main face and the second main face; preparing a wrapped body by wrapping the holding sealing material (10, 10a, 10b) around the exhaust gas treating body such that either the first main face or the second main face of the holding sealing material (10, 10a, 10b) contacts the exhaust gas treating body; and press-fitting the wrapped body into a casing in the same direction as the direction of the shear stress applied to the main face of the holding sealing material (10, 10a, 10b) which is in contact with the exhaust gas treating body. producing the holding sealing material (10, 10a, 10b) by a method for producing a holding sealing material (10, 10a, 10b) comprising: a material mat preparing step of preparing a material mat (100, 110) that comprises inorganic fibers and has a mat shape with a first main face (101, 111), a second main face (102, 112) opposite to the first main face, side faces along a longitudinal direction of the material mat, and end faces along a width direction perpendicular to the longitudinal direction; and a deformation step of plastically deforming the material mat (100, 110) by immobilizing the first main face (101, 111) and the second main face (102, 112) of the material mat, and applying a shear stress to the first main face (101, 111) and the second main face (102, 112) respectively in mutually opposite directions along the width direction, wherein the material mat (100, 110) prepared in the material mat preparing step is a material mat impregnated with an organic binder solution, and in the deformation step, the material mat (100, 110) is immobilized and dried while the shear stress is applied to the first main face and the second main face; a material mat preparing step of preparing a material mat (100, 110) that comprises inorganic fibers and has a mat shape with a first main face (101, 111), a second main face (102, 112) opposite to the first main face, side faces along a longitudinal direction of the material mat, and end faces along a width direction perpendicular to the longitudinal direction; and a deformation step of plastically deforming the material mat (100, 110) by immobilizing the first main face (101, 111) and the second main face (102, 112) of the material mat, and applying a shear stress to the first main face (101, 111) and the second main face (102, 112) respectively in mutually opposite directions along the width direction, preparing a wrapped body by wrapping the holding sealing material (10, 10a, 10b) around the exhaust gas treating body such that either the first main face or the second main face of the holding sealing material (10, 10a, 10b) contacts the exhaust gas treating body; and press-fitting the wrapped body into a casing in the same direction as the direction of the shear stress applied to the main face of the holding sealing material (10, 10a, 10b) which is in contact with the exhaust gas treating body.