A polyacetal resin composition which is suppressed low in formaldehyde generation, while having high stiffness and high toughness. The resin is produced by a method including blending from 0.1 part by weight to 2 parts by weight (inclusive) of a polyacetal copolymer having a branched or crosslinked structure, which is a copolymer of a trioxane, a compound having from 3 to 4 (inclusive) cyclic ether units in each molecule and a compound having one cyclic ether unit in each molecule, per 100 parts by weight of a linear polyacetal copolymer which contains an oxymethylene unit as a main constituent, while containing, as a comonomer unit, an oxyalkylene unit at a ratio of from 0.4% by mole to 0.9% by mole (inclusive) relative to the constituents of the linear polyacetal copolymer, the linear polyacetal copolymer being obtained by copolymerization wherein a heteropolyacid or the like is used as a polymerization catalyst.