To provide a combustion device that prevents an unstable burning state of a burning section in a system of small burning capacity, when the burning sections of different systems are simultaneously burned.

This combustion device 1 includes burning systems for hot water supply and air heating, which can be burned independently from each other, and each combustion system includes one burning section 5, 7, an air supply/exhaust passage, and a fuel supply flow channel 14. The fuel supply flow channel 14 includes a gas proportional valve 16, 17 and a solenoid valve 13, to adjust a fuel supply amount by changing a substantial opening state of the gas proportional valve 16, 17 and increase/reduce a fuel area of the combustion section by opening and closing the solenoid valve 13. Blowers 9, 10 are disposed in the air supply/exhaust passages, and the blower 9 on the hot water supply side is provided with an electric current detecting means 36. When the increase of flow channel resistance is detected by the electric current detecting means 36, a lower limit part in a control range of the gas proportional valve 17 on the air heating side and the blower 10 is raised.