A plant disease controlling agent containing a lactic acid bacterium which is capable of controlling plant disease and a plant disease controlling method which comprises treating a plant and/or soil with the above-mentioned lactic acid bacterium. By using the lactic acid bacterium seemingly advantageous to human health, an agricultural crop can be safely and stably produced. As the lactic acid bacterium as mentioned above, use may be favorably made of a microorganism belonging to the genus Pediococcus such as Pediococcus pentosaceus or a microorganism belonging to the genus Lactobacillus such as Lactobacillus plantarum.
