Provided are a flavor-improving agent capable of improving a tea beverage or a tea-containing food product so as to have a more natural and good-quality flavor that does not feel artificial, and a flavor-improving method for a tea beverage or a tea-containing food product using said flavor-improving agent. This flavor-improving agent for a tea beverage or a tea-containing food product is characterized by comprising isoeugenol. This flavor-improving method for a tea beverage or a tea-containing food product is characterized in that said flavor-improving agent is added in the amount of 0.001 ppb to 100 ppm.
