A fungicidal composition is provided. A fungicidal composition comprising synergistically effective amounts of (a) a carboxylic acid amide derivative of the formula (I) or its salt:wherein B is a heterocyclic group which may be substituted each of R1and R2which are independent of each other, is alkyl X is halogen, alkyl or alkoxy and n is an integer of from 0 to 5, and (b) at least one fungicidal compound selected from the group consisting of an azole compound, an anilinopyrimidine compound, a triazolopyrimidine compound, a strobilurin compound, an N-halogenothioalkyl compound, a pyridinamine compound, a bicarbonate, an inorganic sulfur compound, a dithiocarbamate compound, an organic chlorine compound, a dicarboxyimide compound, an amine compound, a phenylpyrrole compound, a benzophenone compound, a dinitrobenzene compound, a piperidine compound, a morpholine compound, etc.本發明提供一種殺真菌性組成物。殺真菌性組成物包含協乘有效量之(a)式(I)之羧酸醯胺衍生物或其鹽:其中B為可取代之雜環基;各R1及R2彼此獨立為烷基;X為鹵素、烷基或烷氧基;及n為從0至5之整數,及(b)至少一種殺真菌性化合物,其係選自唑化合物、苯胺嘧啶化合物、三唑並嘧啶化合物、史托比系(strobilurin)化合物、N-鹵代硫烷基化合物、吡啶胺化合物、碳酸氫鹽、無機硫化合物、二硫代胺基甲酸鹽化合物、有機氯化合物、二羧基醯亞胺化合物、胺化合物、苯基吡咯化合物、二苯基酮化合物、二硝苯化合物、哌啶化合物、嗎啉化合物等。