The present invention provides a method of improving the flavor of yeast cells including a step of reacting the yeast cells with protease or cellulase, and a food quality improvement agent containing yeast cells as an active ingredient in which the flavor is improved by the method of improving the flavor.本發明係一種具備使蛋白酶或纖維素酶與酵母細胞反應之步驟之酵母細胞之風味改善方法、及含有藉由上述風味改善方法而改善風味之酵母細胞作為有效成分之食品品質改良劑。