Provided is a taste-improving agent that suppresses the unpleasant taste of potassium, such as harshness, irritativeness, and bitterness without reducing the salty taste of a potassium-containing food or drink. The taste-improving agent for a potassium-containing food or drink comprises a lactic acid-fermented yeast extract that is obtainable by fermenting a yeast extract with a lactic acid bacterium and contains 7.5 (w/w) % or more of lactic acid relative to the solid content of the yeast extract.
