A gas combustion type driving tool drives a fastener by combustion pressure when mixed gas of combustible gas and compressed air in a combustion chamber is ignited. The gas combustion type driving tool includes an air ejection valve, and a gas ejection valve. The air ejection valve is configured to eject compressed air into the combustion chamber. The gas ejection valve is configured to eject combustible gas into the combustion chamber. Output related to driving of a fastener is adjustable by adjusting at least one of filling pressure of compressed air or filling pressure of combustible gas.