In a multilayer pressure container constructed by covering a thin wall container made of synthetic resin or the like with a resin-impregnated fiber-reinforced layer and subsequently curing the impregnating resin, the present invention provides a sealing structure for a high-pressure container which allows sealing measures to be phased in during assembly before curing. The sealing structure for a high-pressure container 1 includes a resin liner 2 adapted to contain gas or liquid; a fiber-reinforced plastic layer 3 adapted to reinforce an outside face of the resin liner 2; and a metal mouthpiece 4 used to pour and discharge the gas or liquid, protruding outside the fiber-reinforced plastic layer 3, wherein a filler neck 21 for the gas or liquid is formed on the resin liner 2, protruding outward from inside the high-pressure container, coupling structures 23 and 43 are formed on a protrusion of the filler neck 21 and the mouthpiece 4, and the mouthpiece 4 is coupled with the resin liner 2 by means of the coupling structures 23 and 43 so as to cover the filler neck 21.