PURPOSE: Methanol is used as a raw material and it is brought into contact with a specific catalyst at a specified temperature and pressure and the product is separated by distillation, thus producing title compound used as a reagent in high selectivity with low energy consumption and inexpensive facility costs.

CONSTITUTION: Methanol is brought into contact with a catalyst of sulfonic acid type strong cation exchange resin at 120W160, preferably 130W150°C, and a pressure of over 20, preferably 25W50 atmospheric pressure. Then the pressure is reduced to 6W20, preferably 8W12 atmospheric pressure and distillation is conducted to separate dimethyl ether from methanol and water, thus producing dimethyl ether. The reaction is substantially effected in an adiabatic system to cause advantage of permitting the simplification of the reactor and utilizing the reaction heat to preheat the starting materials.

EFFECT: Side reactions such as decomposition does not take place and the separation and purification steps can be simplified because only distillation gives high purity product enough to be applied directly to various kinds of uses.

USE: Refrigerant and aerosol propellant.