A gasket for sealing a gap between a through hole formed on a wall body and a pipe to be inserted into the through hole, the gasket being provided for the pipe and made of tubular elastic material, the gasket having an inner circumferential lip portion which elastically contacts an outer circumferential face of the pipe; and an outer circumferential lip portion which elastically contacts an inner circumferential face of the through hole; an inner seal area on an inner circumferential side where the inner circumferential lip portion is provided is located at a position so that the inner seal area does not overlap in a radial direction with an outer seal area of an outer circumferential side where the outer circumferential lip portion is provided.