A novel microorganism which can be expected to have both a preventive effect and a therapeutic effect and may be applied to various phytopathogenic bacteria, and whose effects are not reduced even when used in combination with a chemical pesticide, and a plant disease control agent using the microorganism are provided.A Bacillus subtilis strain KS1 (NITE BP-569) which is a novel microorganism and a plant disease control agent including the culture and/or the microorganism bacterial cell of the microorganism as an active ingredient are provided.
