PURPOSE: To improve the operating efficiency, by setting the working condition combining the working parameters including 'the impact number of a bit, the rotation frequency, the feeding speed, and the like, depending on the detected values of the working state, and carrying out a full automatic drilling.

CONSTITUTION: When a selected sort of working is carried out, the operator decides the operating direction, and he selects whether a bit 11 is advanced or retreated in the drilling work, for example. And the working condition by combining plural working parameters is set automatically depending on the detected values of the working state, and some work is carried out fully automatically depending on the sort of working. In this case, when the working state is converted, and the working state detected values are changed, the working condition is corrected one by one according to the variation, and the working condition is reset. For example, a good working condition is gived to all the process of drilling corresponding to the variation when the hardness of the rock-bed is changed on the way of the drilling work. And when a manual regulation is necessary according to the sort of working, the operator makes a minute regulation of each working parameter.