PROBLEM TO BE SOLVED: To provide a method for producing a beverage containing an extract of a plant of genus Salacia, characterized by thermal sterilization of the extract in a manner to keep &alpha-glucosidase inhibiting activity even in an aqueous solution of pH 5-7 or thereabout.SOLUTION: The method for producing the beverage having an &alpha-glucosidase inhibiting activity of an aqueous solution of &ge80% after thermal sterilization process compared with the aqueous solution before thermal sterilization process, includes a thermal sterilization of an aqueous solution containing 0.01-0.60 wt.% of an extract of a plant of the genus Salacia at &ge130°C and &le140°C while setting an F value to &le40 and pH of the aqueous solution to &ge4.5 and &le7.
