The present invention is to provide a composition for preventing 
plant diseases which comprises at least Component I and 
Component II, is capable of obtaining a synergic effect that cannot be expected with each 
single component, is capable of markedly increasing a 
control effect in a much smaller amount of chemicals against various 
plant pathogens, and causes no 
phytotoxicity suffering.A composition for preventing 
plant diseases comprises Components I and II as active ingredients. The Component I is (RS)—N-[2-(1,3-dimethylbutyl)thiophen-3-yl]-1-methyl-3-tri fluoromethyl-1H-
pyrazole-4-
carboxamide. As the 
Component II, there can be exemplified, for example, tetraconazole, flutriafol, imibenconazole, 
triadimefon, 
simeconazole, oxpoconazole fumarate, prothioconazole, 
bupirimate, spiroxamine, metiram, dodine, anilazine, chlozolinate, oxycarboxin, ethaboxam, iprovalicarb, pyrazophos, fluoroimide, diflumetorim, fenhexamid, 
famoxadone, 
fenamidone, cyazofamid, zoxamide, cyflufenamid, boscalid, 
benthiavalicarb-
isopropyl, picoxystrobin, pyraclostrobin, fluoxastrobin or dimoxystrobin.