The present invention provides a broadleaf perennial weed control agent for grass, which has a powerful herbicide effect on weeds that have proven difficult to control with conventional herbicides for grass and/or on weeds having resistance to conventional herbicides, and yet is safe for use on grasses; and a method for controlling broadleaf perennial weeds in grass by applying the control agent to the soil or the foliage.The present invention provides a broadleaf perennial weed control agent for grass, including a 1,5-diphenyl-1H-1,2,4-triazole-3-carboxamide derivative represented by a formula (1) as an active ingredient, and a method for controlling broadleaf perennial weeds in grass that includes applying the control agent to the soil or foliage: wherein R represents an alkyl group of 1 to 10 carbon atoms that may be substituted with a fluorine atom and the like, X1 represents a halogen atom or an alkyl group of 1 to 3 carbon atoms, X2 represents a hydrogen atom or a halogen atom, and Y1 and Y2 each independently represents a hydrogen atom or a fluorine atom.