To prevent the boundary surface separation of a joint filler from a joint internal wall surface to heighten work efficiency by laying to use a joint gasket and improve durability compared with the case of filling only the joint filler.

A joint gasket is continuously formed of hard material such as hard rubber, synthetic resin or polyethylene resin (partially including a closed cell or open cell sponge body). A support 2 is erected on the upper face 1 of an enlarged bottom plate part, and an expansive receiving plate 3 and an expansive through-hole covering plate 31 are continuously formed on the upper side of the support 2. Extension preventing plates 7 of required shape for the interior of U-shape parts on both sides of the support 2 are extended, and the enlarged bottom plate has partition-formed discharge passages of recessed groove shape.