The invention aims to provide an automatic loading device which comprises two carriages which are arranged oppositely in a left-right mode. Smooth sliding base plates are arranged at the bottoms inside the carriages, the bottom of the middle of the two carriages is provided with a transport cart, the top of the transport cart is provided with a sliding plate, and the left end and the right end of the sliding plate each are provided with a side sliding plate integrated with the sliding plate, the top of the sliding plate is provided with a sliding block, a sliding driving motor is arranged at the bottom inside the sliding block, a rotating motor is arranged in the sliding block and located above the sliding driving motor, the top of the rotating motor is provided with a rotating rod, the top of the rotating rod is connected with a rotating block, and the left side and the right side of the rotating block are provided with material supporting plates. First cargoes are placed on the material supporting plates, the height of the sliding plate is adjusted through a lifting motor to be flush with the sliding base plate, the sliding driving motor is started, the sliding block slides to the sliding base plate in the carriage from the side sliding plate and then enters the carriage to send the cargoes to a required position, loading can be performed efficiently and quickly, and the automatic loading device is suitable for cargo loading.