A high-pressure vessel for a vehicle, the high-pressure vessel comprising: a plastic liner including a through hole provided thereon; a plastic sealing member, a portion of which is positioned in the through hole and a remaining portion of which overlaps with the plastic liner, wherein the portion overlapping with the plastic liner is combined with the plastic liner by thermal bonding; a metallic nozzle boss combined with the plastic sealing member so as to cover the portion of the plastic sealing member overlapping with the plastic liner; and a composite material layer combined with the plastic liner and the metallic nozzle boss so as to cover the plastic liner and the metallic nozzle boss; the high-pressure vessel for a vehicle wherein the plastic sealing member includes a cylindrical part positioned in the through hole of the plastic liner and protruding in an outer side direction of the plastic liner, and a wing part of a circular plate shape provided to bend so as to correspond a shape of the plastic liner while extending in a radial direction from an end of the cylindrical part and a predetermined section of which is combined with an outer surface of the plastic liner by the thermal bonding; wherein the metallic nozzle boss is screwed to the plastic sealing member; and characterised in that a major portion of a lower surface of the metallic nozzle boss, which faces the plastic liner, is in contact with the plastic sealing member and only some portion thereof is in contact with the plastic liner. a plastic liner including a through hole provided thereon; a plastic sealing member, a portion of which is positioned in the through hole and a remaining portion of which overlaps with the plastic liner, wherein the portion overlapping with the plastic liner is combined with the plastic liner by thermal bonding; a metallic nozzle boss combined with the plastic sealing member so as to cover the portion of the plastic sealing member overlapping with the plastic liner; and a composite material layer combined with the plastic liner and the metallic nozzle boss so as to cover the plastic liner and the metallic nozzle boss; the high-pressure vessel for a vehicle wherein the plastic sealing member includes a cylindrical part positioned in the through hole of the plastic liner and protruding in an outer side direction of the plastic liner, and a wing part of a circular plate shape provided to bend so as to correspond a shape of the plastic liner while extending in a radial direction from an end of the cylindrical part and a predetermined section of which is combined with an outer surface of the plastic liner by the thermal bonding; wherein the metallic nozzle boss is screwed to the plastic sealing member; and characterised in that a major portion of a lower surface of the metallic nozzle boss, which faces the plastic liner, is in contact with the plastic sealing member and only some portion thereof is in contact with the plastic liner. the plastic sealing member includes a cylindrical part positioned in the through hole of the plastic liner and protruding in an outer side direction of the plastic liner, and a wing part of a circular plate shape provided to bend so as to correspond a shape of the plastic liner while extending in a radial direction from an end of the cylindrical part and a predetermined section of which is combined with an outer surface of the plastic liner by the thermal bonding; wherein the metallic nozzle boss is screwed to the plastic sealing member; and characterised in that a major portion of a lower surface of the metallic nozzle boss, which faces the plastic liner, is in contact with the plastic sealing member and only some portion thereof is in contact with the plastic liner.