NOVELTY - Continuous preparation of alkyl ester of higher fatty acid from free fatty acid containing fatty acid triglyceride-starting mixture in at least one reactor (2), comprises: (a) continuously adding the starting mixture into the reactor; (b) continuously adding at least one monoalcohol into the reactor; (c) at least partially esterifying the free fatty acid with the monoalcohol; (d) at least partially transesterifying the fatty acid triglyceride with the monoalcohol; and (e) continuously removing the formed alkyl ester.    USE - The method and device are useful for continuous preparation of alkyl ester of higher fatty acid from free fatty acid containing fatty acid triglyceride-starting mixture (claimed). The method is useful for preparing biodiesel.    ADVANTAGE - The method prepares large quantities of biodiesel in a cost-effective, environmentally friendly, less time consuming and effortless manner.    DETAILED DESCRIPTION - Continuous preparation of alkyl ester of higher fatty acid from free fatty acid containing fatty acid triglyceride-starting mixture in at least one reactor (2) (which comprises, in vertical direction, a lower region (3), a middle region (4) arranged above the lower region, and an upper region (5) arranged above the middle region), comprises: (a) continuously adding the starting mixture into the reactor through a means, for adding the fatty acid triglyceride mixture, arranged in the upper region; (b) continuously adding at least one monoalcohol into the reactor through a means, for adding the monoalcohol, arranged in the upper region; (c) at least partially esterifying the free fatty acid with the monoalcohol in a packed bed (7) arranged in the middle region; (d) at least partially transesterifying the fatty acid triglyceride with the monoalcohol in the packed bed; and (e) continuously removing the formed alkyl ester through a means, for removing alkyl ester, arranged in the lower region. An INDEPENDENT CLAIM is included for a device, for continuous preparation of alkyl ester of higher fatty acid from free fatty acid containing fatty acid triglyceride-starting mixture, comprising the reactor as above per se, at least one means, for continuous addition of the starting mixture, arranged on the upper region, a layer of filling elements (preferably a layer of inert filling elements including ceramic material, glass or plastic) arranged in the middle region, at least one means, for continuous addition of monoalcohol into the reactor, arranged in the lower region and at least one means, for continuous removal of alkyl ester from the reactor, arranged in the lower region.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic representation of a device for continuous preparation of alkyl ester of higher fatty acid.    Reactor (2)    Lower region (3)    Middle region (4)    Upper region (5)    Packed bed. (7)