Disclosed is a method which can readily design an agricultural chemical-containing resin composition having a desired release rate history and can produce the agricultural chemical-containing resin composition. Specifically disclosed is a method for producing an agricultural chemical-containing resin composition, including: respectively selecting an acetamiprid content AcSA and a hydrophilic white carbon content CaSA in the composition relative to the total mass of acetamiprid, a styrene-maleic anhydride copolymer or a styrene-maleic anhydride copolymer-mixed resin, and hydrophilic white carbon, so as to satisfy the inequations of: 0.524×AcSA+1.422×CaSA−6.009≦40% by mass, 5% by mass≦AcSA≦35% by mass, and CaSA≧0.1% by mass; and mixing the acetamiprid, the styrene-maleic anhydride copolymer or the styrene-maleic anhydride copolymer-mixed resin, and the hydrophilic white carbon, so that the thus selected contents AcSA and CaSA can be achieved.