THE PRESENT INVENTION PROVIDES A COMPOSITION IN WHICH A FUNGICIDAL EFFECT AGAINST A CULTIVATED CROP INFECTED BY A PLANT DISEASE IS STABLE AND HIGHLY ACTIVE. AN EXCELLENT AGRICULTURAL OR HORTICULTURAL FUNGICIDE COMPOSITION FOR CONTROLLING A PLANT DISEASE IS PROVIDED BY USING (A) AT LEAST ONE IMIDAZOLE COMPOUND REPRESENTED BY FORMULA (I): WHEREIN R REPRESENTS A C1-6 ALKYL GROUP OR A C1-6 ALKOXY GROUP AND N REPRESENTS AN INTEGER OF 1 TO 5 AND (B) POLYOXINS AS ACTIVE INGREDIENTS BY COMBINATION AS COMPARED TO A SINGLE USE OF EACH COMPOUND, AND A PLANT DISEASE IS THEREBY CONTROLLED.