A pressure vessel capable of securely sealing a mouth ring with a liner portion, and being manufactured at low costs. A boss seal part 112 is provided in a liner portion 11 of the pressure vessel, and an inner peripheral surface of a boss part 20 of a mouth ring 2 is covered with the boss seal part 112. A boss-side collar part 114 is provided in the boss seal part 112 so as to project outwardly, and a sealing member 4 composed of a resilient body is disposed in a space between an inner peripheral surface of the boss seal part 112 and an outer peripheral surface of the valve 3.