A method of winding a holding sealing material includes providing a mat-shaped holding sealing material including inorganic fibers. An exhaust gas treating body is provided having cell walls extending along a longitudinal direction of the exhaust gas treating body to define cells. The mat-shaped holding sealing material is wound around an outer peripheral portion of the exhaust gas treating body to form multiple layers including a first layer and a second layer wound around the first layer. Each of the multiple layers is shifted along the longitudinal direction in a winding order such that the first layer is placed closer to one end face of the exhaust gas treating body than the second layer. A shift between the first layer and the second layer is from about 0.15% to about 15% of a length in a width direction of the holding sealing material.