To compressively deform a gasket for a joint in a normal condition in the joint and bring out the best sealability regardless of the assembling ways of an architectural panel.

A gasket 10 for a joint is made of an elastic and hollow extruded molding like foamed silicone rubber and attached along the outer peripheral face of an architectural panel 1 to seal the clearance (joint) between adjacently arranged architectural panels 1. And the gasket 10 is provided with a base 11 attached along the outer peripheral face of the architectural panel 1, a seal part 12 provided with a nearly semicircular and hollow section and projected on the base 11 and integrally formed, and a reinforcing part 13 formed thick at the inside corner between the base 11 and the seal part 12. Since the lower part of the hollow seal part 12 is reinforced by the reinforcing part 13 and the elastic force against lateral directions is enhanced, even when such an architectural panel that a lateral force acts on the hollow seal part 12, is assembled, the gascket prevents the panel from falling sideways and it is compressively deformed in a normal condition.