The present invention relates to 1,2,3-thiadiazole compounds represented by formula (I): wherein R 1 , R 2 , R 3 , R 4 and R 5 each represents H, halogen, CN, alkyl, alkoxyalkyl, aryl, arylalkyl, alkylcarbonyl or the like R 6 represents -C=(W 1 )YR 7 in which R 7 reresents H, alkyl, alkenyl, phenylcarbonyl, heterocyclic ring-carbonyl, arylsulfonyl or the like Y represents O, S, -N(R 11 ), -N(R 11 )O- in which R 11 represents H, alkyl, cycloalkyl, substituted phenyl, or the like W 1 represents O or S and symbols in the formula are defined in detail in the specification or salts thereof, and to a plant disease control agent for agricultural and horticultural use which contains the compound as an active ingredient.