The utility model discloses a three-roller enclosed welding device, which comprises a bottom plate, a left inclined plate and a right inclined plate, wherein the left inclined plate is fixed on the bottom plate, and extends inwards and upwards simultaneously; the right inclined plate is fixed on the bottom plate, and extends inwards and upwards simultaneously; the bottom plate is provided a lower roller extruding device; the left inclined plate is provided with a left roller extruding device; the right side inclined plate is provided with a right roller extruding device; and the lower roller extruding device, the left roller extruding device and the right roller extruding device construct an extruding hole. The three-roller enclosed welding device disclosed by the utility model has the advantages of simple and compact structure, high efficiency, small floor area, high pressure accuracy and high position accuracy due to the adoption of three rollers for extruding steel tubes, convenience in adjusting the extruding force, suitability for welding of steel tubes of various specifications, and good steel tube welding line quality.