To provide a method for treating cut grass at a low cost whereby cut grass is quickly treated without influencing the environment and recurs to nature, without attempting an eliminating treatment, e.g. incineration, or the production of high-cost goods by e.g. compaction or fermentation.

Cut grass P weeded out, a decomposing bacillus S composed of Bacillus subtilis, and a pressure-sensitive adhesive N are put in an agitation vessel 2 containing water, and the cut grass P is finely crushed with a working face 5 to give a liquid matter W. If the liquid matter W is delivered with a pump 7 and then sprayed by a worker with a hose 8 on a weeded bank 10 or a flood plane 11, the component of the crushed cut grass P is decomposed by the decomposing bacillus S mixed in the liquid matter W, becomes nourishment together with water in the liquid matter W, and is returned as fertilizer to soil and weeds. The adhesive N decreases the scattering of the liquid matter W during spraying, making the work easy.