PURPOSE: To enhance workability by inserting a guide body in guide holes beforehand bored in a rock, regulating a lateral directional movement of a bit fitted and installed in the guide body, and boring a desired hole along the guide holes.

CONSTITUTION: Plural guide holes 11 are bored at equal intervals in a straight line on an excavating surface so that adjacent center cut holes 10 overlap with each other. Next, a rock drilling tool 1 is installed on a rock drill, and a guide rod 5 is inserted in the guide holes 11, and a button bit 2 is fitted and installed in an end part of the rod 5 projecting from a boring surface 12. Next, rotary motion and axial directional reciprocating motion are applied to the bit 2, and a rock is frictionally crushed, and is collapsed, and a hole 10 is formed. In this case, the bit 2 is supported with the rod 5 inserted in the holes 11, and since a lateral directional movement is regulated, the hole 10 is straightly bored along the holes 11. Compressed air is blown out of a clearance between a hole 2a of the bit and the rod 5, and cuttings are blown off. Therefore, an accurate hole which does not cause a lateral unintentional movement can be efficiently formed.