A gas chromatograph is provided which is capable of effectively reducing the amount consumed of a carrier gas, reducing the time and effort required for an operator to manually set parameters, and preventing damages to a column and a detector due to a setting mistake. In a case where a stop operation for the power supply of the gas chromatograph is performed (Yes in step S101), the flow rate of a carrier gas to be supplied to a sample vaporization chamber is decreased and the temperatures of the column and the detector are sufficiently lowered (steps S102 to S104), and then the power supply of the gas chromatograph is switched over from an ON state to an OFF state (step S106).