A method for producing a polyacetal resin composition, comprising: adding a compound (d) which is a carbonate, hydrogen carbonate, or carboxylate of an alkali metal element or an alkaline earth metal element or a hydrate thereof or a hydroxide of an alkali metal element or an alkaline earth metal element to a reaction product prepared by copolymerization of trioxane as a main monomer (a) and a cyclic ether and/or cyclic formal having at least one carbon-carbon bond as a comonomer (b) using a heteropoly acid represented by Formula as a polymerization catalyst (c); melt-kneading the mixture to deactivate the polymerization catalyst (c) and prepare a polyacetal copolymer; and adding 0.002 parts by weight or more and 0.1 parts by weight or less of an aliphatic polycarboxylic acid (e) having four or more carbons and two or more carboxyl groups and 0.01 parts by weight or more and 0.5 parts by weight or less of a hindered phenolic antioxidant (f) to 100 parts by weight of the polyacetal copolymer, H m [M 1 x ·M 2 y O z]·nH 2 O where M 1 represents a central element composed of one or two elements selected from P and Si; M 2 represents one or more coordination elements selected from W, Mo, and V; and x represents an integer of 1 or more and 10 or less, y represents an integer of 6 or more and 40 or less, z represents an integer of 10 or more and 100 or less, m represents an integer of 1 or more, and n represents an integer of 0 or more and 50 or less. adding a compound (d) which is a carbonate, hydrogen carbonate, or carboxylate of an alkali metal element or an alkaline earth metal element or a hydrate thereof or a hydroxide of an alkali metal element or an alkaline earth metal element to a reaction product prepared by copolymerization of trioxane as a main monomer (a) and a cyclic ether and/or cyclic formal having at least one carbon-carbon bond as a comonomer (b) using a heteropoly acid represented by Formula as a polymerization catalyst (c); melt-kneading the mixture to deactivate the polymerization catalyst (c) and prepare a polyacetal copolymer; and adding 0.002 parts by weight or more and 0.1 parts by weight or less of an aliphatic polycarboxylic acid (e) having four or more carbons and two or more carboxyl groups and 0.01 parts by weight or more and 0.5 parts by weight or less of a hindered phenolic antioxidant (f) to 100 parts by weight of the polyacetal copolymer, H m [M 1 x ·M 2 y O z]·nH 2 O where M 1 represents a central element composed of one or two elements selected from P and Si; M 2 represents one or more coordination elements selected from W, Mo, and V; and x represents an integer of 1 or more and 10 or less, y represents an integer of 6 or more and 40 or less, z represents an integer of 10 or more and 100 or less, m represents an integer of 1 or more, and n represents an integer of 0 or more and 50 or less. where M 1 represents a central element composed of one or two elements selected from P and Si; M 2 represents one or more coordination elements selected from W, Mo, and V; and x represents an integer of 1 or more and 10 or less, y represents an integer of 6 or more and 40 or less, z represents an integer of 10 or more and 100 or less, m represents an integer of 1 or more, and n represents an integer of 0 or more and 50 or less.