To provide a holding seal material which can be kept wound around exhaust gas treating material even if being a holding seal material of high density and can prevent displacement thereof when accommodating an exhaust gas treating body wound around the holding seal material in a casing.

A holding seal material comprises a mat material containing inorganic fiber. The holding seal material includes a first and second side parts which are substantially rectangular in a plane view and parallel to each other in a longitudinal direction, and keeps a recessed and projected fitting parts which are disposed perpendicular to each other in a longitudinal direction. At least one hooking part is formed on each of the first and second side parts.