The invention provides an automatic digging device for tree transplantation. The automatic digging device comprises a tree ring, fixed pin plates, chutes, side chutes, a nozzle, a built-in telescopicrod, a digging motor, a digging gear disc, a storage battery, a remote control device, a triangular earth collector, a rack lever, a triangular groove and a side groove hole, wherein two groups of fixed pin plates are integrally arranged at the bottom of the outer end of the tree ring; through holes are formed in two sides of the fixed pin plates; the chutes are formed in the middle of the top ofthe tree ring, and the side chutes are formed in two sides of the chutes; a connecting groove and a connecting block are respectively arranged at two ends of the tree ring; two groups of screw holes are formed in the connecting groove; and two groups of through holes are formed in the middle of the connecting block. Due to the arrangement of the chutes, slide blocks and moving wheels, rotary moving ability is provided for the digging device, the moving position of the digging device is limited, the digging device is ensured to move according to a desired track, the digging efficiency is effectively improved, and the manual labor is greatly saved.