The present invention relates to a water-floating large-sized granular agricultural chemical composition that employs a plastic microballoon as a floating carrier, a method for producing a water-floating large-sized granular agricultural chemical composition quickly and stably with good quality, and the method. It is an object of the present invention to provide a manufactured water-floating large-sized granular agricultural chemical composition with good quality. The manufacturing method of the granular agrochemical composition which solved the said subject contains an agrochemical active ingredient, surfactant, a hollow body, and a solid support, and the particle size whose particle size is 3 mm or more is 80% or more. A method for producing a granular agrochemical composition having a distribution and a property of floating on the water surface and collapsing on the water surface within 30 minutes, comprising a hollow body, a thermoplastic polymer as a wall material, and an average particle diameter of 1-100 μm The surface of an already expanded plastic microballoon is coated with mineral fine powder having an average particle size of 0.1-15 μm and 1/2 or less of the expanded plastic microballoon, and the expanded mineral micropowder coated inflatable plastic microballoon Used, the mineral fine powder coated expanded plastic microballoon is mixed with an agrochemical active ingredient, a surfactant and a solid carrier, and then a predetermined amount of water is added to the mixture and kneaded. The kneaded product is extruded and granulated from a screen having a pore diameter of 3 mm or more, and then the obtained granulated product is dried to remove moisture.本発明は、浮遊性担体としてプラスチックマイクロバルーンを採用する水面浮遊性大型粒状農薬組成物において、迅速にかつ安定的に品質良好な水面浮遊性大型粒状農薬組成物を製造する方法、並びに該方法により製造された品質良好な水面浮遊性大型粒状農薬組成物を提供することを課題とする。 当該課題を解決した粒状農薬組成物の製造方法は、農薬活性成分と、界面活性剤と、中空体と、固体担体とを含有してなり、粒径３ｍｍ以上のものが８０％以上である粒度分布と、水面に浮遊し、かつ３０分以内に水面で崩壊する性質を有する粒状農薬組成物の製造方法であって、中空体として、熱可塑性高分子を壁材とし、平均粒子径１－１００μｍである既膨張プラスチ
