PURPOSE: To produce the titled fuel which has excellent energy conversion efficiency and whose consumption can be saved, by bringing ionized air passed through an air-ionizing apparatus into contact with a liquid fuel.

CONSTITUTION: After dust is removed from air in an air cleaner 1, air is dehydrated in a dryer 2, and passed through a high-pressure bomb 3 and then an air- ionizing apparatus 4 wherein a carbon layer provided on the inner periphery of a cylindrical metallic protective tube is a negative electrode and a stick-shaped metal fixed to the axis of said tube is a positive electrode, whereby air is ionized and the ionized air is stored in a tank 8. The ionized air is led through a pressure buffer device 9 and a solenoid valve 10 to the bottom of a tank 12 and atomized through a lot of through-holes provided on an air atomizer 13 into a liquid fuel 11, whereby the ionized air is brought into contact with the fuel to form an ionized fuel which is then discharged from an outlet 14.