Process for producing oxymethylene copolymer

The present invention is to provide a process for producing an oxymethylene copolymer, in which deteriorate due to oxidation hardly occurs, an amount of formaldehyde generated from the product, in particular, an amount of formaldehyde generated from the product when stored for a long time under environment of high temperature and high humidity is reduced, and occurrence of mold deposit during molding is small. More specifically, provided is a process for producing an oxymethylene copolymer which comprises Step 1 of polymerizing polymer raw materials containing trioxane and a comonomer in the presence of a specific amount of an acid catalyst, Step 2 of adding a hydroxylamine compound represented by the following general formula (1): wherein R 1 and R 2 are as defined in the claims and the specification, to a product obtained in the Step 1 in an amount of 1 to 20-fold mol based on an amount of the acid catalyst and mixing these, and Step 3 of further melting and kneading a mixture of the product and the hydroxylamine compound obtained in the Step 2.