The present invention provides a method for controlling weeds in paddy rice cultivation, which comprises steps of: applying a water-diluted solution comprising a herbicidal compound such as 1-(2-chloro-6-propylimidazo[1,2- b ]pyridazin-3-ylsulfonyl)-3-(4,6-dimethoxypyrimidin-2-yl)urea to a paddy field and flooding the paddy field within the first week after the application of the herbicidal compound.
