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.習用多種殺真菌組成物具有實務上的問題，以致於視施用位置而有預防或治療效果不足、殘餘效果不足、或對植物疾病的控制效果不足的情形，因而需要一種能夠克服這些問題的殺真菌組成物。本發明提供一種殺真菌組成物，含有式(I)之酸醯胺衍生物或其鹽類作為活性成分：其中A為可被取代之苯基、可被取代之苄基、可被取代之萘基、可被取代之雜環狀環、可被取代之稠合雜環狀環、或類似基團；B為可被取代之雜環狀環、可被取代之稠合雜環狀環、或可被取代之萘基；R1與R2各彼此獨立為烷基或類似基團；R3為氫或類似基團；W1與W2各彼此獨立為氧或硫。
