To prevent overlapping of mats even when displacement occurs therebetween.

A holding sealing material 10 includes a mat 11 including an inorganic fibrous material. In a plan view, the mat 11 has a basic quadrangular shape consisting of long sides extending in a longitudinal direction and short sides substantially perpendicular to the long sides. The mat 11 has a recessed portion 13b formed at one of the short sides and a projected portion 13a formed at another of the short sides, whereby the projected portion 13a of the mat 11 can be fitted to the recessed portion 13b of the mat 11 as the mat 11 is rolled around a member to be wrapped. The shape of a cross-section perpendicular to a longitudinal direction of the projected portion 13a is a shape of a quadrangle with a portion cut out which includes at least one corner on the side of the member to be wrapped, or a shape of a cross-section perpendicular to the longitudinal direction of the projected portion 13a or the recessed portion 13 b is a shape with a potion cut out which includes another corner of the quadrangle.