PURPOSE: To ensure maximal use under the conditions of various rocks of a rock drill while carrying out the remote control of connection release in the case of a slot drill.

CONSTITUTION: The drill device operates a drill steel-tool assembly capable of being rotated and reciprocated. A reversible motor 50 is connected to a percussion bar 3, and turns a drill steel-tool. The percussion bar is percussed by a percussion piston 10. A rotary fluid valve 15 operates the piston. Connectable and releasable couplings 37, 38, 43 couple the valve 15 and the percussion bar 3 together with the motor under a normal state. The motor 50 operates only the percussion piston for extracting the drill steel-tool, or revolves only the percussion bar for clamping or releasing a drill rod in a specific mode.