Abstract: A method for producing fatty acid methyl ester has steps of providing waste oil with a fatty acid; proceeding a first, second and third esterification; and proceeding transesterification to obtain the fatty acid methyl ester. Because the method of the present invention uses low cost waste oil as a raw material, cost of fatty acid methyl ester can be decreased. Moreover, an amount of free fatty acid in the waste oil can be reduced by esterification, therefore, waste oil used in the transesterification has lowered amount of free fatty acid. Accordingly, the method has increased yield of fatty acid methyl ester.