To provide a fixture which is used in a cover device for hermetically sealing a pipe penetration part of a wall, having air-tightness and water-tightness under high pressure.

A cover device for hermetically sealing a pipe penetration part of a wall, includes a hermetic seal sheet wound in a cylindrical shape and covering between a pipe opening portion of a sleeve fitted into a through hole of a pipe penetration part of a construction wall and a pipe part of a pipe passing through the pipe opening portion, and is constituted by fixing both cylindrical openings of the cylindrical seal sheet to the pipe opening portion of the sleeve and/or the pipe part of the pipe by a plurality of fixing parts. A fixture is used for the cover device and includes a belt-like member pressing onto and fastening the hermetic seal sheet, and connection parts provided in both respective ends of the belt-like member. An area of a side of the belt-like member which contacts with and presses onto the hermetic seal sheet is smaller than an area of a side opposite to the side of the belt-like member which contacts with the hermetic seal sheet.