Abstract: A polyoxymethylene composition which is remarkably improved in heat stability, little stains molds even in long-term continuous molding and little generates formaldehydic stench in molding, and which comprises a polyoxymethylene and, added thereto, 0.01 to 5% by weight of an antioxidant and 0.01 to 10% by weight of a melamine-formaldehyde polycondensate, each based on the polyoxymethylene, characterized in that the melamine-formaldehyde polycondensate used is one which is prepared mainly from melamine and formaldehyde and contains 2.0 to 10 moles of the melamine units on the average per mol of the melamine-formaldehyde polycondensate, wherein the mean mole number of hydrogen bonded to 3 moles of the amino groups contained in 1 mole of melamine is 3.0 moles or above.