A method for supplying a fluorine gas-containing gas from supply equipment for supplying the fluorine gas-containing gas to consumption equipment consuming the fluorine gas-containing gas, the supply equipment including a filled container filled with a first fluorine gas-containing gas, a pipe letting a container valve of the filled container and the consumption equipment communicate with each other, and a pressure regulator provided on the pipe and passing the gas from an upstream side to a downstream side while regulating a gas pressure, the method comprising performing a sealing step of bringing the pressure regulator into a closed state, characterized in that the supply equipment further comprises a buffer tank connected to a portion on an upstream side relative to the pressure regulator of the pipe, and the method comprises, after the sealing step, introducing a second fluorine gas-containing gas having a fluorine gas concentration in a range of ±10% of a fluorine gas concentration of the first fluorine gas-containing gas into a portion between the container valve and the pressure regulator of the pipe such that a pressure is lower than the gas pressure in the filled container, and after the sealing step, in a state where the second fluorine gas-containing gas is sealed in the portion between the container valve and the pressure regulator of the pipe and after the buffer tank is brought into an opened state, introducing the first fluorine gas-containing gas from the filled container into the portion between the container valve and the pressure regulator of the pipe, bringing the pressure regulator into an opened state, and then supplying the first fluorine gas-containing gas to the consumption equipment while regulating a pressure by the pressure regulator. the supply equipment including a filled container filled with a first fluorine gas-containing gas, a pipe letting a container valve of the filled container and the consumption equipment communicate with each other, and a pressure regulator provided on the pipe and passing the gas from an upstream side to a downstream side while regulating a gas pressure, the method comprising performing a sealing step of bringing the pressure regulator into a closed state, characterized in that the supply equipment further comprises a buffer tank connected to a portion on an upstream side relative to the pressure regulator of the pipe, and the method comprises, after the sealing step, introducing a second fluorine gas-containing gas having a fluorine gas concentration in a range of ±10% of a fluorine gas concentration of the first fluorine gas-containing gas into a portion between the container valve and the pressure regulator of the pipe such that a pressure is lower than the gas pressure in the filled container, and after the sealing step, in a state where the second fluorine gas-containing gas is sealed in the portion between the container valve and the pressure regulator of the pipe and after the buffer tank is brought into an opened state, introducing the first fluorine gas-containing gas from the filled container into the portion between the container valve and the pressure regulator of the pipe, bringing the pressure regulator into an opened state, and then supplying the first fluorine gas-containing gas to the consumption equipment while regulating a pressure by the pressure regulator.