Abstract: A method and an apparatus for dosing the air-fuel mixture in burners of the type which is formed with an evaporator tube (9) through which fuel and some amount of combustion air is introduced in the combustion chamber (1) and in said combustion chamber is mixed with further combustion air and is inflamed. The optimum amount of combustion air is determined for different amounts of fuel and for different reference temperatures in a predetermined point of the evaporator tube (9) adjacent the mouth (10) thereof in the combustion chamber (1), and the temperature of the air-fuel mixture is measured by means of a thermo element (41) in the said point of the evaporator tube (9).