TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: The quantity of water used during neutralization is 1-20 mol equivalent of amount of sulfate to produce.Preferred Process: Lower alcohol is added in the range of 50 mass% of the whole amount of the reaction liquid mixture, and the viscosity of reaction liquid mixture during neutralization is adjusted. The filtrate is distilled under reduced pressure.Preferred Catalyst: The alkali catalyst is potassium hydroxide.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The quantity of water used during neutralization is 1-20 mol equivalent of amount of sulfate to produce.Preferred Process: Lower alcohol is added in the range of 50 mass% of the whole amount of the reaction liquid mixture, and the viscosity of reaction liquid mixture during neutralization is adjusted. The filtrate is distilled under reduced pressure.Preferred Catalyst: The alkali catalyst is potassium hydroxide.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Alcohol: The lower alcohol is methyl alcohol. EXAMPLE - A waste edible oil having an acid value of 3, an iodine number of 105, a flash point of 230degreesC, a moisture content of 1% and an ash content of 1.3%, was used as raw material oil. The raw material oil was mixed with a solution obtained by dissolving potassium hydroxide as a catalyst (in kg) (13) in methyl alcohol (solvent) (122), and reacted at 65degreesC for 15 minutes. A concentrated sulfuric acid (12) diluted with water (6.4) was dripped over the reaction mixture, and stirred. The obtained mixture was diluted with methyl alcohol (50 l), and left for 1 hour. Precipitation of potassium sulfate hydrate crystal was confirmed. The resulting solution was subjected to suction filtration, and filtrate was distilled at 50-100degreesC and 100 mmHg and at 100-220degreesC. The resulting product was separated into alkyl ester layer and glycerol layer, and high-purity glycerol was obtained at high yield. Thus, eco-friendly bio-diesel fuel was produced at reduced manufacturing cost.