Provided are: a composition containing 96-99 area % of eicosapentaenoic acid alkyl ester, the composition having an arachidonic acid alkyl ester content of 0.7 area % or less, and an eicosapentaenoic-acid-alkyl-ester mono-trans isomer content of 2.5 area % or less; and a method for producing a composition containing a high concentration of eicosapentaenoic acid alkyl ester, the method including performing precision distillation on a composition containing eicosapentaenoic acid alkyl ester, obtained by alkyl esterification of a raw material oil containing eicosapentaenoic acid, under a vacuum of 0.2 Torr or lower and a temperature of 190° C. or lower in the entire column, and performing a concentration treatment on the precision-distilled composition using chromatography.