To provide a drilling method and device therefor proper to use for drilling a ground such as a clay layer, a silt layer difficult to conduct a drilling with a conventional drilling device.

A bit, to which cuttings inflow port, in which cuttings are made to flow into a front end section and sent rearwarded, is formed, is installed at the front end section of a drilling rod connected to a rock drill, and a pipe, in which a front end section is engaged with the head section of the bit and which is rotated together with the bit, is fitted externally and mounted outside the drilling rod. The drilling is conducted, imparting a rotation, a strike and a thrust to the bit while the cuttings generated by the drilling are made to flow into the pipe from the cuttings inflow port for the bit by a high-pressure fluid discharged from the head section of the bit, moved backwards through the inside of the pipe and discharged to the outside from the rear end section of the pipe.