A dead cell of a lactic acid bacterium or a culture containing the dead cell is added to a dairy product (e.g., a yoghurt, a cheese, a milk beverage) in an amount of 0.001 wt% or more in terms of the dry weight of the dead cell. It becomes possible to enhance the proliferation of a lactic acid bacterium, to shorten the time required for fermentation of a lactic acid bacterium, and to improve the survivability of a lactic acid bacterium during storage over a long period, without affecting the flavor or production cost of the finished product.
