The invention discloses a static mechanical automatic vertical drilling tool achieving zero-deflecting under the vertical posture. The static mechanical automatic vertical drilling tool includes an outer cylinder, a piston base which is connected with the outer cylinder, and a pendulum cylinder. A mandrel and upper disk valves are arranged in the outer cylinder, a lower disk valve is arranged on the piston base, the mandrel is connected with the outer cylinder, and the upper disk valves are rotatably connected with the lower disk valve. The pendulum cylinder, located between the outer cylinderand the mandrel, is capable of controlling the opening and closing of the upper disk valves, and the pendulum cylinder is rotatably connected with the outer cylinder. The static mechanical automaticvertical drilling tool is high in well deflection control precision and sensitivity, deviation correction limit is close to theoretical verticality, the deflecting phenomenon cannot happen, and the well deflection control precision and the using performance of the mechanical automatic vertical drilling tool are enhanced.