An automatic mechanical arm device consists of a portal frame, a synchronous belt transmission mechanism, a guide rod, a main air cylinder, a fixing frame, a connecting seat and pneumatic sucking discs, wherein the portal frame is formed by welding square tubes and of a rectangular structure, the upper portion of the portal frame is provided with the synchronous belt transmission mechanism, the guide rod and the main air cylinder are installed in the middle of the portal frame, the main air cylinder is connected with the fixing frame, the lower portion of the fixing frame is provided with the connecting seat, N pneumatic sucking discs are installed at the lower end of the connecting seat, and the synchronous belt transmission mechanism is moved to a finished product working table after the pneumatic sucking discs suck finished product materials, and the working efficiency is improved. The automatic mechanical arm device has the advantages that the device is used for collecting punching type mechanical products after product processing is finished and is especially suitable for taking-up of large-size materials after punching is finished, punched products are orderly after being collected, the working utilization rate is improved, and the like.