In order to provide sweetpotato condensed extract (that is imo-mitsu) as a dietary supplement having a feeling of high quality with emphasis on nutritional functionality, which is obtained from sweetpotato, does not have extraneous flavors or odor of malt, and also improve taste and flavor enables the setting of a long periods for consumption and storage, a method for producing a imo-mitsu composition adds β-amylase contained in liquid from squeezing sweetpotato or from sweetpotato dry powder as saccharifying enzyme to a raw ingredient derived from sweetpotato by adding water and heating processing, and performs saccharification processing by heating at 60 to 75° C. for 30 to 60 minutes.
