A hydraulic pushing device, including: a hydraulic unit, a rear seat, a front seat, a prying mechanism, an automatic adjustment mechanism, and a zero-torque pushing mechanism. The hydraulic unit and the rear seat are disposed on a platform. The zero-torque pushing mechanism includes two hydraulic cylinders, one end of each of the two hydraulic cylinders is hinged to the rear seat via a third hinge pin, and the other end of each of the two hydraulic cylinders is hinged to the front seat via a second hinge pin. The automatic adjustment mechanism includes a control lever and two locating pieces. One end of the control lever is in a fixed connection to the front seat, and the other end of the control lever is clamped by the two locating pieces. The prying mechanism includes two pawls, a pawl shaft, two prying guides, and two rows of equidistantly-disposed stop pieces.