NOVELTY - The apparatus has micro-bubble generation apparatus (3) that generates microbubble of fuel tank (2). A fuel flow path connects micro-bubble generation apparatus and fuel tank. The HHO gas of HHO gas generation device (1) and liquid fuel of fuel tank are introduced into micro-bubble generation apparatus. The composite fuel which disperses micro-bubble of HHO gas in liquid fuel is generated. The circular flow path (4) introduces liquid fuel in fuel tank into micro-bubble generation apparatus while introducing composite fuel into fuel tank through fuel flow path.    USE - Manufacturing apparatus of HHO gas micro-bubble composite fuel supplied to internal combustion engine such as diesel engine for motor vehicle e.g. diesel car, boat and ship. Can also be used in agricultural machine such as tractor, cultivator, generator with engine, rice transplanter, rice-reaping machine, brush cutting machine, and aircraft, and construction and building machines.    ADVANTAGE - Since the circular flow path introduces liquid fuel in fuel tank into micro-bubble generation apparatus while introducing composite fuel into fuel tank through fuel flow path, the combustion efficiency is improved without carrying out additional processing to the engine and fuel consumption can be ensured.    DETAILED DESCRIPTION - The apparatus has HHO gas generation devices that are electrolytic cell which stores electrolyte solution including water as main component, and two or more sets of electrodes comprised by anode and cathode. An airtight cover seals upper end of electrolytic cell. Electrolyzer electrolyzes and generates HHO gas by sending electric current between anode and cathode using power supply device. The HHO gas is introduced into micro-bubble generation apparatus from the ejection opening equipped with the current control apparatus.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the manufacturing apparatus of HHO gas micro-bubble composite fuel.    HHO gas generation device (1)    Fuel tank (2)    Micro-bubble generation apparatus (3)    Fuel flow path (4)    Non-return valve (8)