Friction stir welding device with detector for detecting torque current of friction stir welding tool

A machining device comprising five axial kinetic coordinate systems that can be controlled simultaneously, three axes of which, are linear moving axes and two axes of which are rotary axes, with one axis of the five axes being provided with a tool rotating function, whereby said machining device is equipped with a cutting tool 51 and a friction stir welding tool 52. The current value observed when a large-diameter portion of said tool 52 contacts the work object is set in advance, and by observing the torque current of the rotary shaft of the tool 52 during friction stir welding, the insertion depth of the tool 52 can be controlled by maintaining the observed torque current above the preset current value, thus providing a good weld. A single device can provide both the cutting and the welding. Thus, it is possible to reduce equipment cost, installation space, plant area, lead time and production cost.