A dead cell of a lactic acid bacterium or a culture containing the dead cell of a lactic acid bacterium is added to the dairy products such as yogurt, cheese, milk beverage or the like in an amount of 0.001 wt % or more in dry weight of the dead cell, therefore, it is possible to enhance the growth of a lactic acid bacterium, to shorten the time required for fermentation, and to improve the viability of a lactic acid bacterium during storage over a long period, without affecting the flavor or production cost of the dairy product.