A high-pressure tank is provided capable of simply and inexpensively suppressing gas leaks under low temperature condition. The high-pressure tank 10 comprises a tank main body 11 having the opening part 13, in which high-pressure gas is filled, and the reinforcement member 12 covering the outer surface of the tank main body 11 and reinforcing the tank main body 11. The tank main body 11 is provided with the outer projecting part 15 being uncovered with the reinforcement member 12 at a position different from the opening part 13. This outer projecting part 15 is heated from the outside of the tank main body 11 by the electric heater 30 to heat the tank main body 11, and thereby suppressing degradation of the sealing properties of the seal member 22.