NOVELTY - The bio-diesel fuel production apparatus (10) has a transesterification unit (1) to mix a catalyst containing an alcohol solution with oil and fat and to acquire a reaction product. A depressurizing-distillation unit (2) distills a low boiling substance from the reaction product and obtains a residual liquor. A gravity-separation unit (3) separates the residual liquor into a light liquid and heavy liquid. A purification unit has several detachable purification units (4,5) to make the light liquid to contact a solid absorbent and purifies the light liquid.    USE - For producing bio-diesel fuel such as fatty acid alkyl ester bio-diesel fuel used for diesel engine, from vegetable oil and fat such as rapeseed oil, soy bean oil, palm oil, palm kernel oil, rice bran oil, sunflower oil, sesame oil, corn oil, coconut oil, safflower oil, peanut oil, cottonseed oil, linseed oil, mustard oil, etc., and animal oil and fat such as beef tallow and lard, whale oil, fish oil, etc.    ADVANTAGE - The bio-diesel fuel is manufactured easily and rapidly, at low cost. The size of the apparatus is reduced. The installation cost and the manufacturing cost are reduced.    DETAILED DESCRIPTION - The purification units has several through holes formed in the region in which the solid absorbent is filled. The solid absorbent in one of the purification unit is chosen from silica gel, activated clay, Florisil, activated carbon, alumina, and activated alumina or mixtures. The solid absorbent in another purification unit is chosen from silica gel, activated carbon, zeolite, molecular sieve, sodium sulfate, magnesium sulfate, calcium chloride, alcohol absorption resin and water absorption resin. The filling amount of the solid absorbent with respect to the reference light liquid is 0.5-10weight%. An INDEPENDENT CLAIM is included for bio-diesel fuel manufacturing method which involves mixing a catalyst containing an alcohol solution with oil and fat. The boiling substance is distilled from the reaction product and a residual liquor is obtained. The obtained residual liquor is separated into a light liquid and a heavy liquid. The light liquid is made to contact a solid absorbent and the light liquid is purified so that a fatty acid alkyl ester bio-diesel fuel is obtained. The light liquid obtained from the residual liquor has a moisture content of 500 ppm or less, acid value of 0.5 mgKOH/g or less, methanol value of 2000 ppm or less, total glycerol value of 2500 ppm or less and an alkali metal value of 5 mg/kg or less.    DESCRIPTION OF DRAWING(S) - The figure shows a conceptual diagram of the bio-diesel fuel production apparatus. (Drawing includes non-English language text)    Transesterification unit (1)    Low boiling substance depressurizing-distillation unit (2)    Gravity-separation unit (3)    Purification units (4,5)    Bio-diesel fuel production apparatus (10)