To realize the combustion capable of reducing the generation of NOx by realizing pre-vaporization of liquid fuel, pre-mixing combustion of gas fuel/liquid fuel and slow combustion in low oxygen concentration on the basis of the effect of combustion gas recirculation.

A circular container 1 of a double tube composed of an inner cylindrical part 1i and an outer cylindrical part 1o respectively closed at their one end is applied as a combustion chamber, an inflow channel 5 is penetrated through an outer peripheral side face (outer cylindrical part 1o) of the circular container 1 to form the flow of the air flowing with a speed component from an opened end 1x to a closed end part 1t of the circular container 1, and a fuel nozzle 4 is mounted inside of the closed end part 1t of the circular container for injecting the fuel in the direction (direction opposite to flow of air) from the closed end part 1t to the opened end 1x of the circular container 1 with an expanding angle α to a radial outer side with respect to a central axis J of the circular container 1, toward the inflow channel 5.