[Problem] Provided is a material that is capable of suppressing the loss of carbonation in a carbonated beverage over time to reduce changes in flavor, including mouthfeel, when drinking the beverage.[Solution] Addition of a water-soluble soybean polysaccharide into a non-alcoholic carbonated beverage suppresses the loss of carbonation over time to retain carbonation in the carbonated beverage for a long period of time, thereby reducing changes in flavor during a period from immediately after opening the container thereof to when drinking the beverage after storage.