A tight-seal construction provided with a metal seal and a holding plate composed of a thin plate having a through window portion. A hitching concave peripheral groove is formed on a peripheral face of the metal seal, and the metal seal is held by the holding plate having a claw portion hitching to the concave peripheral groove and provided with a strap elastic portion protruding from an inner peripheral end edge of the through window portion as to freely and elastically deform in axial directions and radial directions.