To provide a drill mechanism for a blasting rock drill capable of safely conducting the work and sharply reducing the cost.

This drill mechanism for the blasting rock drill is provided with a rod base 16 moved and driven in the longitudinal direction of a guide shell by the cutting power shaft 12 of the rock drill, a center rod 20 fitted with a cutting bit 18 at the extension tip, a small-diameter side rod 22 fitted with the cutting bit 18 at the extension tip, and a rod support section 24 provided on the guide shell and rotatably supporting the center rod 20 and the side rod 22. The rod base 16 includes a main shaft 26 screwed and fixed with the cutting power shaft 12 of the rock drill and the center rod 20 respectively and a sub-shaft 28 inserted and fixed with the side rod 22 into a barrel portion. A spur gear 30 is formed on the peripheral face of the main shaft 26, a cylindrical head portion is provided on the rock drill side of the barrel portion of the sub-shaft 28, and a spur gear 32 meshed with the spur gear 30 of the main shaft 26 is formed on the peripheral face of the head portion.