Disclosed is a herbicidal composition comprising a compound represented by formula (I) or its salt, wherein the substituents are as disclosed within the specification, and a polyoxyalkylene alkyl ether phosphate or its salt. Further disclosed is a method for improving the herbicidal effect of the compound of formula (I) or its salt, and a method for controlling undesired plants comprising applying a herbicidally effective amount of said herbicidal composition.
