To provide a combustion system capable of keeping a good and stable combustion condition even in a lean mixed gas, sufficiently attaining reduction of fuel consumption, NOx and CO and being widely applied to various combustion systems by improving the atomized state of the fuel during fuel injection.

A gas-mixed and dissolved fuel is prepared in advance by mixing and dissolving the gas in a requisite ratio into the liquid fuel to be fed to a combustion chamber through a gas-dissolving nozzle in a gas dissolver. The fuel is transferred from the gas dissolver to another low pressure or air-opened fuel tank and taken out of the tank. The fuel is pressurized and sprayed into a low pressure combustion chamber through a spray nozzle 2 and ignited and burned in the atomized state.