A paddy seed treatment agent containing a herbicidal active component and having a sufficient herbicidal effect, while having a reduced risk of herbicide injury to paddy rice, a method for treating paddy seeds using the paddy seed treatment agent, paddy seeds, and a method for controlling paddy field weeds by sowing and cultivating the paddy seeds, are provided. The paddy seed treatment agent contains fenquinotrione or a salt thereof as a herbicidal active component. The method for controlling paddy field weeds includes sowing and cultivating paddy seeds treated with this paddy seed treatment agent, and the like.
