PURPOSE: To provide a liquid fuel combustion promoter, capable of promoting combustion and improving combustion efficiency or reducing fuel consumption and purifying exhaust gas due to the promotion of combustion and the improvement of combustion efficiency and no harm to man and beast.

CONSTITUTION: An α-ray emitting rod type body 3, formed of a sintered material, containing the principal constituent of tungsten and the balance of about 2wt.% of thorium oxide, is attached to the inner wall surface 9 of an air supplying tube 2 near the mixing position of fuel and air for a liquid fuel combustion device 1 for mixing liquid fuel with air immediately before an ignition plug while fine amount of α-rays radiated out of the α-ray emitting rod type body 3 and having ionization effect and/or the radio waves of α-ray zone having strong ionization effect are projected against air, passing through the air supplying tube 2.