A holding sealing material includes a plurality of mats. The plurality of mats have a longitudinal direction and include a lower mat and an upper mat laminated on the lower mat. Each of the plurality of mats includes inorganic fibers and has a substantially rectangular shape. A length of the lower mat in the longitudinal direction is longer than a length of the upper mat in the longitudinal direction. Each of the plurality of mats is connected to each other at at least two fixed portions. The at least two fixed portions are positioned at different positions in the longitudinal direction.