The invention provides a plate-integrated gasket which can reduce a width necessary for installing seal members provided in a plurality of plates which are laminated on each other, and can achieve an improvement of productivity. In order to achieve this purpose, in the plate-integrated gasket, one plate and the other plate are laminated on each other, an outer peripheral surface of the one plate is fitted or loosely fitted to a stepped surface which is formed in the other plate, and a seal member made of an elastic material having a rubber-like elasticity is integrally formed astride both of the one plate and the other plate, and has a fixed portion filled in a seal fixing groove which is formed between the one plate and the other plate.