Abstract: To provide a process for stable and continuous production of a polyacetal resin, mainly comprising a copolymer of 1,3-dioxolane and trioxane under the presence of a catalyst, in a high yield on an industrial scale for a long period of time. In the continuous production of a polyacetal resin by mixing 1,3-dioxolane with boron trifluoride and/or a coordination compound of boron trifluoride and then, mixing the obtained mixture with trioxane to conduct bulk polymerization in a polymerization machine, 1,3-dioxolane is brought into contact with boron trifluoride and/or a coordination compound of boron trifluoride while feeding both at the same direction and they are mixed together for 0.1 to 30 seconds under the condition of at least 0.1 m/sec of the linear velocity of the mixture and subsequently mixed with trioxane.