To drive a nail accurately into a prepared hole bored while a crack or the like in nailing are prevented by boring preliminarily the prepared hole through a member to be worked.

A bearing 11 is fixed to a lower end part of a wrist part 10 of a robot, and a shaft 12 is, in a freely pivotal manner, supported with the bearing 11. Arms 13, 14 are fixed onto an outer peripheral surface of the shaft 12. A drill device 15 is fitted to one side arm 13 and a nailing machine 16 is respectively fitted to the other side arm 14. Then, in nailing the shaft 12 is made to pivot with a rotary actuator as not shown in the figure, and the drill device 15 is located at a specific position to bore a prepared hole on a member to be worked. Thereafter, the shaft 12 is made to pivot reversely, and the nailing machine 16 is located so that an axial center of the nail to be driven conforms to the prepared hole position. Then, nailing is executed.