The invention relates to a method of manufacturing polyacetal copolymer. The method of manufacturing polyacetal copolymer can effectively manufacture oxygen-resistant and anti-aged polyacetal copolymer. An extruder (A) is provided with a terminal stabilization zone and an antioxidant dispersion zone. The method includes the steps that: a stabilization step: performing terminal stabilization of polyacetal copolymer (1) in the terminal stabilization zone of the extruder (A); a mixing step: mixing polyacetal copolymer (2) with antioxidant in an extruder (B) to obtain a mixture; and a supplying step: supplying the mixture for the polyacetal copolymer (1) after terminal stabilization in the extruder (A) in the antioxidant dispersion zone, wherein the temperature of the resin in the extruder (B) is greater than the melting point of the antioxidant and is less than the melting point of the polyacetal copolymer(2).