A benzimidazole derivative having the formula, ##STR1## wherein R is cyano or thiocarbamoyl; Q is lower alkyl or a group represented by the formula NQ.sup.1 Q.sup.2, in which Q.sup.1 and Q.sup.2 are independently lower alkyl, lower alkyl substituted with phenyl, lower alkenyl or lower alkynyl, or they form a lower alkylene ring when taken together at their ends which ring may include a hereto atom; X is hydrogen or halogen; and Z is a group which consists of (a) one oxygen atom or two non-adjacent oxygen atom, (b) --CF.sub.2 -- group and (c) any one of a single bond, --CF.sub.2 --, --CFH--, CFCl-- and --CH.sub.2 -- groups and forms a five-membered or six membered ring together with two adjacent carbon atoms of the benzene ring; is obtained by reacting a corresponding 2-cyanobenzimidazole compound and a sulfamoyl chloride derivative. The benzimidazole derivative is incorporated into agricultural and horticultural fungicides as an active ingredient.