A holding sealing material includes laminated mats. One or more fixed parts partially combine the mats. Each of the mats has a basic rectangular shape. Each of the mats has a recess on one of shorter sides of the rectangular shape and a projection on another shorter side and is designed to be wound around an object to be wound so that the projection and the recess are fitted to each other. The mats have respective longitudinal lengths that increase as a distance from the object to each of the mats increases. A mat that is placed at a closest position to the object has a shortest longitudinal length. An area of the projection of the mat that is placed at a closest position to the object is smaller than an area of the projection of a mat that is placed at a farthest position from the object.