The invention provides a submerged-arc welding device and a submerged-arc welding method. The submerged-arc welding device comprises a base, a stand column, a supporting shaft and a welding gun, wherein the stand column is vertically arranged on the base; the supporting shaft is horizontally arranged above the base, and the supporting shaft is connected to the stand column in a height-adjustable mode; and the welding gun is vertically connected with the supporting shaft and can rotate in a vertical plane so as to adjust the included angle between the welding gun and the vertical plane where the supporting shaft is located, so that the welding gun is aligned with a welding bead of a to-be-welded workpiece so as to carry out a welding operation. According to the submerged-arc welding deviceand the submerged-arc welding method, when the welding operation is carried out, according to the position of the welding bead, the height of the welding gun and the angle between the welding gun andthe plane where the welding bead is located can be firstly correspondingly adjusted so that the welding gun can be aligned with the to-be-welded welding bead, and therefore the welding operation can be efficiently and correspondently carried out; and welding quality of a welding product is guaranteed while efficiency of the welding operation is improved.