Abstract: A method of safely controlling a burning of a fuel gas in a combustor in response to the pressure change in a fuel gas sealed in a fuel gas passage between a fuel gas supply source and the combustor communicated with the fuel gas supply source, the method comprising the steps of sealing a fuel gas in the fuel gas passage before supply to the combustor prior to the start of the operation of the combustor, detecting a pressure change in the fuel gas sealed in the fuel gas passage, controlling the supply of the fuel gas to the combustor in response to a signal representing the detected pressure change, and interrupting start of operation of the combustor when a pressure change in the sealed fuel gas is detected prior to the start of the operation of the combustor. Abnormal burning such as an explosion due to fuel gas leakage is prevented.