To provide a composition exhibiting excellent controlling effects on plant diseases.

The plant disease control composition containing a pyridazine compound expressed by formula (I) (wherein, R1 indicates a chlorine atom, a bromine atom, a cyano group, a methyl group, or a methoxy group, R2 indicates a fluorine atom or a hydrogen atom; and R3, R4 each indicate a halogen atom or the like) and one or more kinds of carboxamide compound selected from the group (A) exhibits the excellent controlling effects on the plant diseases. The group (A) includes bixafen, isopyrazam, boscalid, fluopyram, fluxapyroxad, sedaxane, penflufen, flutolanil, mepronil, carboxin, thifluzamide, penthiopyrad and furametpyr.