The object of the present invention is to provide a microorganism which places little burden on the environment, shows an extremely low possibility of a resistant pathogenic bacterium to emerge, and has a superior controlling ability against various plant diseases (in particular, soft rot and canker of leaf and root vegetables); a plant disease controlling agent containing the microorganism; and a method for controlling plant diseases comprising applying the plant disease controlling agent to the plant and/or the grove soil thereof. A plant disease controlling agent is used which contains a bacterial cell of Pseudomonas rhodesiae having controlling ability against plant diseases, preferably a bacterial cell of Pseudomonas rhodesiae FERM BP-10912 or its variant having controlling ability against plant diseases.