The invention discloses a full-automatic plate material mounting mechanical arm device. The full-automatic plate material mounting mechanical arm device comprises a plate material conveyer, a portal frame, a first cart and a second cart, wherein a first speed reducing motor is arranged on the portal frame, a sliding rod and a screw rod are horizontally arranged on the portal frame from top to bottom in sequence, and the two ends of the sliding rod are fixedly connected to the portal frame. One end of the screw rod is rotationally connected to the portal frame, the other end of the screw rod isfixedly connected with an output shaft of the first speed reducing motor, the screw rod is in threaded connection with a lifting plate, the lifting plate is in sliding connection with the sliding rod, and a mechanical arm is arranged at the lower end of the hanging plate. The mechanical arm comprises a mounting plate, wherein a fixing plate is fixedly connected to the end, away from the lifting plate, of the mounting plate, and a second speed reducing motor is installed on the fixing plate. The full-automatic plate material mounting mechanical arm device is stable in structure, simple in operation, scientific and reasonable in design, and short in production period; and the mechanical arm is convenient to lift and adjust, so that the plate materials are clamped conveniently, and thereby the full-automatic production can be realized.