NOVELTY - A raw material containing alkali catalyst (3), oil (1) and alcohol (2) is transesterified to obtain crude biodiesel fuel (4) and crude glycerin (10). The crude biodiesel fuel and glycerin are separated by specific gravity difference method. Refined glycerine (5) is dissolved with crude biodiesel fuel by mixing and stirring. Then, mixture is re-separated to increase the purity of fatty acid ester in crude biodiesel fuel. The fatty acid ester is washed using solvent of soluble constituent of glycerin. Thus, manufacture of biodiesel fuel is carried out.    USE - Manufacture of biodiesel fuel used as petroleum alternative fuel and fertilizer.    ADVANTAGE - The method efficiently and economically provides biodiesel fuel without discarding large quantity of substance during manufacture.    DETAILED DESCRIPTION - A raw material containing alkali catalyst, oil and alcohol is transesterified to obtain crude biodiesel fuel and crude glycerin. The crude biodiesel fuel contains fatty acid ester as a main component. The fatty acid ester contains alkali catalyst, alcohol, fatty acid soap, water, glycerin, and glyceride as impurities. The crude glycerin contains glycerin as main component including free fatty acid and alkali catalyst. The crude biodiesel fuel and crude glycerin are separated by specific gravity difference method. Refined glycerine is dissolved with crude biodiesel fuel by mixing and stirring, such that the water-soluble impurities such as alkali catalyst are dissolved in the crude biodiesel fuel. The mixture is re-separated using specific gravity difference method to increase the purity of fatty acid ester in crude biodiesel fuel. The fatty acid ester is washed using the solvent of the soluble component of glycerin. Thus, the manufacture of the biodiesel fuel is carried out.    DESCRIPTION OF DRAWING(S) - The drawing shows the block diagram illustrating the manufacturing process of the biodiesel fuel. (Drawing includes non-English language text)    Fats and oils (1)    Alcohol (2)    Alkali catalyst (3)    Crude biodiesel fuel (4)    Refined glycerin (5)    Crude glycerin (10)