<p>A combustion stabilizing device (100) applicable to a gas engine (1) is provided with the following: a methane value calculation unit (61) for calculating the methane value for a gas fuel; an air-supply adjusting unit (70) for adjusting the pressure and temperature of air supplied to a main chamber (33); and an air-supply control unit (62) for controlling the air-supply adjusting unit (70). The air-supply control unit (62) sets an air-supply pressure correction value or air-supply temperature correction value in accordance with the gas-fuel methane value calculated by the methane value calculation unit (61), and controls the air-supply adjusting unit (70) so that the air-supply pressure or air-supply temperature is corrected only by the set correction value.</p>
