PURPOSE: To prevent damage and defective soldering even if the soldering position is slightly shifted by fitting a soldering iron to a mobile mechanism via a parallel spring means formed so as to make parallel movement freely restorably relatively with respect to other parts.

CONSTITUTION: Since the soldering iron 3 is fitted to the mobile mechanism such as an articulated robot via the parallel spring means 5, the iron tip is moved in the parallel direction to displacement of the parallel spring means 5 and brought into contact with a work 7, by which even if the mobile mechanism further continues operation, the movement of the iron tip stops, soldering is performed in this state and soldering can be always performed under the proper contact pressure. Accordingly, even when a printed wiring board is not properly fixed and held, excessive force is not acted on the iron tip and the work, the occurrence of damage of each part can be reduced and the occurrence of defective soldering also can be reduced by setting the teaching position deeply in the progressing direction of the iron tip.