PURPOSE: To obtain a means fit for digging the bottom of a hole having very small diameter such as a footing hole and capable of shifting the direction forward and backward or to the right and left and changing the place in the narrow bottom of the hole by no use of a running device such as wheels or tracks.

CONSTITUTION: A boom 9 turnable around a vertical shaft 6 and a horizontal shaft 8 is provided on a machine body 5, while at the tip part of the boom 9 being provided an arm 11 turnable around a horizontal shaft 10. A power excavator 29 formed by mounting a bucket or a pick hammer 13 or the like trunable around a horizontal shaft 12 at the tip part of the arm 11 is placed on the bottom 28 of the hole and a part of the machine body 5 is lifted by pressing down the tip part of the arm 11 to the bottom 28. By turning the boom 9 or the machine body 5 around the vertical shaft 5 under the conditions, the machine body 5 is moved in the horizontal direction.