To provide a jointing workpiece, its jointing method, and a processing panel which eliminate the need of the outer force restraint against the force for separating members in jointing by the mutual restraint.

In this jointing workpiece, jointing portions 3 of members 2 to be jointed are formed to be a mutual restraint structure 4, which prevents at least the members 2 from being detached in a direction approximately crossing a joint line 5 generated at the time when the members 2 are mutually restrained. Thus, since the members 2 are restrained by the mutual restraint structure 4, and under this condition, are jointed along the joint line 5, there is little need for the restraint by the outer force.