To provide an inexpensive automatic rock drill for rock drilling work which is used by being mounted on a bucket of construction machinery, wherein a manual rock drill is mounted on the liftable or lowerable platform of the automatic rock drill and lifted/lowered by using an electric winch and the gravity of nature, which has the structure of adjusting weight so as to prevent excessive pressure from being applied to a rod bit in drilling, which enables a drilling direction to be operated in both longitudinal and lateral directions by the use of the same manual operation button by virtue of the mounting of an attachment, and which reduces a failure rate by virtue of the simplification of the structure.

The liftable or lowerable platform (4) wherein an adjusting weight (3) is set is passed through a lifting/lowering guide rail (5) wherein two cylinders are attached to a main body mounted on the bucket of a backhoe; the manual rock drill (2) is mounted on the platform (4) and repeatedly lifted/lowered by winding/rewinding by the use of the electric winch (1) which is mounted on the upper part of a mounting body, so that drilling work can be performed. In horizontal drilling, the attachment (12) wherein the adjusting weight (8) is set is set perpendicularly to the main body, and both ends of a weight hanging wire (9) are interlocked by coupling the adjusting weight (8) and the platform (4) of the main body via a pulley. All of the lifting/lowering operations are performed by means of a lifting/lowering operation button (11) of the electric winch.