An equipment main body (2) has an intermediate electrode set (10) that is disposed between upper and lower welding electrodes (5) and provided at least on the upper welding electrode side or the lower welding electrode side. The intermediate electrode set (10) has a plurality of intermediate units (18), each of which has an intermediate electrode set jig (11) and an intermediate electrode (12) that can be attached to and detached from the intermediate electrode set jig (11), the plurality of intermediate units (18) being configured as units of rotary type disposed rotatably in the circumferential direction so as to sequentially stop at the welding positions that correspond to the upper and lower welding electrodes in the vertical direction. Through the intermediate electrodes (12) of the intermediate units (18) at the welding positions, an object is resistance-welded while being pressurized by a pressurizing unit (7).
