To obtain an auger driving device by which large turning force can be transmitted.

A chuck mechanism 72 for grasping an auger drill is formed by a wedge member 54 inserted between an inclined surface 52 formed on a ring member 50 integrated with a rotating member 40 rotated by a driving motor 46, and a round shaft 27 of the auger drill. A key 74 and a key way 76 are formed along the axial direction of the round shaft 27 on the round shaft 27 of the auger drill and the rotating member 40, and the rotation of the rotating member 40 is transmitted to the auger drill by slidable fitting of the key 74 and the key way 76.