The invention provides a method for producing an oxymethylene copolymer including a polymerization step for cationically polymerizing trioxane and a comonomer at a polymerization temperature of from 135 to 300° C. in the presence of at least one salt of a protonic acid having a molecular weight of 1,000 or less, and at least one polymerization initiator selected from the group consisting of protonic acids having a molecular weight of 1,000 or less, protonic acid anhydrides having a molecular weight of 1,000 or less, and protonic acid ester compounds having a molecular weight of 1,000 or less; wherein the total concentration of metal components contained in the trioxane and comonomer used in the polymerization step is 300 ppb by mass or less.