Conventional many fungicidal compositions have had practical problems such that either a preventive effect or a curing effect is inadequate, the residual effect tends to be inadequate, or the controlling effect against plant diseases tends to be inadequate depending upon the application site, and a fungicidal composition to overcome such problems has been desired. The present invention provides a fungicidal composition containing an acid amide derivative of the formula (I) or a salt thereof, as an active ingredient: wherein A is phenyl which may be substituted, benzyl which may be substituted, naphthyl which may be substituted, heterocyclic ring which may be substituted, fused heterocyclic ring which may be substituted, or the like; B is heterocyclic ring which may be substituted, fused heterocyclic ring which may be substituted, or naphthyl which may be substituted; each of R1 and R2 which are independent of each other, is alkyl, or the like; R3 is hydrogen, or the like; each of W1 and W2 which are independent of each other, is oxygen or sulfur.