To provide a method and a device, capable of easily adjusting a drilling position to a center axis of a core drill with high accuracy when a drilling device is set, and excellent in workability.

A laser oscillator 8 is attached to a rotation driving shaft 7 to which a core drill is mounted. A laser beam is projected to a marked drilling position beforehand, and a point irradiated with the laser beam is superposed on a marked point so that the center axis of the core drill is determined and a pedestal 4 is fixed. As for the laser oscillator, an laser oscillator that can be attached to the rotation driving shaft with a magnet is used.