PURPOSE: To propel improving work on any ground by applying a rotating and striking force to a hollow driving drum set for enabling sand to be always cast in the axial core of a boring machine.

CONSTITUTION: On the axial core of a boring machine main-body 2, a hollow driving drum 6 is set to be freely rolled, and both the ends are sealed with a front plate 11 and a rear plate 12 with dust seals 14a fitted on, and a spline section 6a on the outer periphery of the hollow driving drum 6 is slidably fitted on a spline section 9a inside a driving gear 9. Besides, an outer periphery gear section 9b is fitted on a gear 8 fitted firmly on a boring motor 7 fitted on the boring machine main-body 2, and a hollow piston 10 is slidably fitted in a space between the driving drum 6 and the main body 2. Then, a rotating and striking force is applied to the driving dram 6 set for enabling sand to be cast in the axial core. As a result, with a connected hollow casing, ground can be bored through also in an urban district, and work can be executed on any ground.