PURPOSE: To improve the workability of a boring device and reduce the execution cost by installing penetration devices on both the sides of a frame and installing a rotary device on the frame and spreading the diameter of a precedingly drilled hole.

CONSTITUTION: A boring device is constituted of a frame 1, rotary supporting device 10, and penetrating devices 20a and 20b which are installed on both the sides of the frame 1. The penetration device 20a is constituted of a swivel head body 2 fixed on a slide frame 3 which is freely raised and lowered on the frame 1, hydraulic cylinders 4 and 4 installed on both the sides of the swivel head body 2, and a hydraulic chuck 6 for holding a boring rod. After the preceding drilling by using the first boring rod, the frame 1 is revolved by the rotary device 10, and the second boring rod is inserted into the preceding drilled hole, and the diameter is spread. Accordingly, after the first drilling, the diameter spreading drilling work can be executed in succession by one device.