A sealing material composition which comprises sheet-like members containing expanded graphite, and which hardly causes the sheet-like members to be broken is provided.A sealing material composition 1 comprises: a stacked body 5; and a long surrounding body 6 which surrounds the stacked body. The stacked body has a plurality of sheet-like members 10 each of which is formed into a tape-like shape by expanded graphite. In the stacked body, the plurality of sheet-like members are stacked in a direction which intersects with the longitudinal direction of the surrounding body, and, in the plurality of sheet-like members, sheet-like members which are adjacent to each other in the stacking direction are disposed to be displaced from each other in the longitudinal direction of the surrounding body, in a relatively movable manner. The surrounding body allows the adjacent sheet-like members to be relatively moved in the longitudinal direction of the surrounding body, while maintaining the stacked state of the adjacent sheet-like members.