A composition for controlling plant diseases, containing a pyridazine compound represented by Formula (I) and one or more compounds selected from a group (A), exhibits an excellent control effect against plant diseases. The present invention provides a composition for controlling plant diseases, containing the pyridazine compound represented by Formula (I) and one or more compounds selected from a group (A), and a method for controlling plant diseases, including a step of applying an effective amount of the pyridazine compound represented by Formula (I) and one or more compounds selected from a group (A) to a plant or soil for cultivating a plant.Group (A): a group consisting of metalaxyl, mefenoxam (metalaxyl-M), benalaxyl, and kiralaxyl (benalaxyl-M).[In the formula, R1 represents a chlorine atom, a bromine atom, a cyanc group, or a methyl group, and R2 represents a hydrogen atom or a fluorine atom.]
