Disclosed herein is a soil-borne disease control method capable of simply suppressing a soil-borne pathogen. The method for controlling a soil-borne disease includes applying at least one polyhydroxyalkanoic acid having a structure represented by the following formula (1) to soil:[—CHR—CH2—CO—O—] (1)(wherein R is an alkyl group represented by CnH2n+1 and n is an integer of 1 or more but 15 or less).