According to one aspect of the present invention, a hydrogen gas filling method includes receiving, from a vehicle equipped with a tank to be filled with hydrogen gas and powered by the hydrogen gas, a temperature of the tank before a start of filling; calculating a difference between a preset maximum temperature and the temperature of the tank; calculating a filling speed of the hydrogen gas depending on the difference; and filling the hydrogen gas from an accumulator in which the hydrogen gas is accumulated into the tank at the filling speed calculated via a measuring machine.