To provide an automatic drilling device capable of efficiently drilling a hole by making it possible to move a drilling unit while preventing lowering of drilling positional precision of the drilling unit by reducing a working range of the drilling unit.

A guide rail 4 is provided along tables 3a, 3b to respectively fix a plurality of works 2a, 2b an articulated robot 7 installing a drill motor unit 6 on it is moved and stopped at a specified position on this guide rail 4 and drilling work by the drill motor unit 6 is carried out on the works 2a, 2b. It is possible to prevent lowering of the drilling positional precision of the drill motor unit 6 as the working range of the articulated robot 7, that is, a range to carry out the drilling work by the drill motor unit 6 is limited to a narrow range in such a drilling work.