Parasitic plants parasitizing on crops can be controlled effectively, by providing an agent for controlling parasitic plants, which comprises tiadinil or the like as the active ingredient and a method for using an agent for controlling parasitic plants, which comprises treating a parasitized plant or soil with an effective amount of agent for controlling parasitic plants. As a result, the yield of crops can be recovered to the level of parasitism-free crops. Additionally, by inhibiting parasitism of parasitic plants strongly, development of the next generation can be inhibited so that the level of pollution with parasitic plants on agricultural land can be lowered with cultivating sensitive crops.