The invention discloses a rotary welding device, comprising a frame as well as a drive component and a rotary component which are fixed on the frame. The rotary welding device is characterized in that the rotary component comprises a fixed disk fixed on the frame and a rotary disk rotationally installed on the fixed disk; the fixed disk is also equipped with a support rolling device which comprises a riding wheel rotationally installed on the fixed disk; and the riding wheel is positioned between the fixed disk and the rotary disk and is matched with the rotary disk. The rotary disk is provided with a soft steel wire clamping slot on which a soft steel wire rope is sleeved, and two ends of the soft steel wire rope are respectively connected with the drive component. The rotary welding device disclosed by the invention is reasonable in design and reliable in performance, ensures that the rotary disk can rotate more flexibly in a more balanceable mode when loading the rotation of a large-sized workpiece, can obtain good welding quality, has high work efficiency, lightens labor intensity of workers, and is convenient and safe in operation and maintenance.