PURPOSE: To easily and accurately set the drilling position and angle of an excavating drill relative to an excavating cross sectional area, and realize a practical method suitable for a work site.

CONSTITUTION: The sighting targets 26 and 27 are laid on the drill frame 20 of a drilling machine 10 to drill a working face with an excavating drill 23, at the prescribed gap in the advancing and retreating directions of the drill 23, and a beam generator 54 is made to transmit a laser beam 54a in parallel to a working face drilling direction. Furthermore, the sighting targets 26 and 27 on the frame 20 are aligned with the laser beam 54a, thereby indexing the drill 23 at a reference position in parallel to the working face drilling direction. Then, the frame 20 is displaced in parallel from the indexed reference position to the drilling position of the working face, and the drill 23 is adjusted to angles in the prescribed horizontal and vertical directions. The drill 23 is thereby set at an angle suitable to drill the working area of a tunnel.