PURPOSE: To perform weeding function effective over long period in only single spraying of herbicide and reduce load of operation by spraying a slow-acting herbicide having high weeding performance and quick-acting herbicide having low weeding performance into a field simultaneously with planting operation of seedling.

CONSTITUTION: Quick-acting herbicide having low weeding performance such as bensulide and low acting herbicide (a) having high weeding performance and obtained by applying an eluting film 21 consisting of paraffin, etc., and readily capable of degrading onto the outer surface of high performance herbicide 20 obtained by adding ethyl 2-methyl-4-chlorophenoxylactate and 2- methylthio-4,6-bisethylamino-S-triazine to bensulide and granulating the mixture are sprayed into a field simultaneously with planting operation of seedling and herbicide having low performance is acted directly after rice transplanting and after planting seedling is grown to certain degree and activity thereof is sufficiently enhance, high performance herbicide is acted and trouble of two time operations are saved without exerting evil influence on the seedling weakened in activity directly after planting.