Novel amidine compounds which may be active ingredients in herbicides that are reliably effective at a lesser dose and highly safe, and herbicides containing these compounds as active ingredients are provided. Amidine compounds represented by a formula (1′) and herbicides containing at least one kind of these compounds as active ingredients, [wherein G is an optionally substituted nitrogen-containing heterocyclic group represented by a formula (2′) with a proviso that the number of carbons constituting the nitrogen-containing heterocycle of the nitrogen-containing heterocyclic group is 10 or less and that 2H-Indazole ring is excluded; Q′ represents cyano or the like; and A′ represents substituted phenyl or the like].