To provide a method for efficiently producing powdery Lactobacillus fermentum of single micron in a high viable cell ratio.

Purified water and pure culture solution of Lactobacillus fermentum, skim milk, a natural salt, molasses, sodium glutamate, dog tooth violet starch and defatted soy flour are mixed under stirring and the Lactobacillus fermentum is proliferated and cultured for a prescribed time therein and then, sprayed and dried by a spray drier set to 150°C to 180°C inlet temperature to produce the powdery lactic acid bacterium having 1 μm to 9 μm average particle diameter.