Abstract: A water-in-oil-type oil-water emulsion fuel which is obtained by mixing heavy oil and water together with sn inorganic component, wherein said inorganic component consists of four kinds of substance of sodium, magnesium, calcium and chlorine, which is characterized in that once the emulsion is obtained, oil-water separation does not occur and the emulsion state is maintained even if any temperature is added in the combustion, and a stable state of the combustion is always attained.