The invention discloses a device for jointly or solely producing refined methanol and dimethyl ether by using crude methanol. The method is to use the crude methanol as a raw material, and produce the dimethyl ether by a method of methanol gas-phase catalytic dehydration, The method comprises the following steps: adding dilute alkali liquor and soft water into a primary tower to carry out pretreatment; regulating pH value; removing light component impurities; extracting primarily distilled impurities and treating the mixture in a vaporization tower. Heavy component impurities in the crude methanol enter a methanol recovery tower along with vaporization tower bottom liquor, and are extracted out from a fusel oil extraction port at the stripping section of the methanol recovery tower; the vaporization tower in the method is a rectifying tower, and the methanol recycled by the methanol recovery tower as backflow ensures purity of the methanol entering methanol vapor of a dehydration reaction system; and the method can jointly or solely produce the dimethyl ether or the refined methanol, and can produce the dimethyl ether and the refined methanol at the same time.