The invention discloses a method for carrying out the leveling of support legs and an automatic leveling device which adopts the method. A horizontal sensor detects tilt angles on two coordinate axis directions, the judgment of the horizontal state of the support legs is carried out according to the tilt angles, the highest support leg or the higher side support leg are found, the lower support leg or the lower side support leg is regulated, and the detection and the judgment are continuously carried out during the regulation process till all the support legs are in the horizontal state. As the leveling, the detection and the judgment are simultaneously carried out and a plurality of support legs are simultaneously regulated during the leveling process, the leveling can be realized more rapidly and more accurately. The invention further provides the automatic leveling device based on the method. The automatic leveling device can be connected with an original manual regulating system in parallel, and the two systems are mutually independent. Therefore, the impact of human factors can be overcome through the automatic leveling, the leveling precision is high, the period is short and the repeatability is high.