To provide a supporting instrument for a rock drill, which can be used even in a steeply slanting mountain or in a woody place, can be easily installed and removed, and can finely adjust a drilling position and a drilling angle.

A tripod for fixing the rock drill is composed of a guide leg 9 and two supporting legs 10, and a guide leg 9 is fitted with a supporting base 11. The length of the supporting leg 10 can be changed by a locating bolt 41, and an angle of the guide leg 9 with respect to ground is made changeable. A jackhammer 7 is fixed to the supporting base 11, which is made to ascend/descend along the guide leg 9 by the turning of an operating rod 13 having a handle 12. A drill rod 5 mounted on the jackhammer 7 drills a hole in the ground or a baserock along the guide leg 9.