The invention relates to an automatic winding device. The automatic winding device mainly comprises a winding mechanism, a rack, an automatic roll changing mechanism, an air swelling shaft transmission mechanism and a tension control system. The winding mechanism is composed of a winding roller, an air swelling shaft, a cycloid motor, synchronous pulleys, an air swelling shaft drive mechanism and an air swelling shaft guide mechanism. The automatic roll changing mechanism is composed of an air pipe, a pull-rod-type cylinder, a carrier roller, a compression roller, a rubber roller, a rodless cylinder and the like. A roll discharging mechanism is composed of a miniature cylinder, a baffle and a spring. The air swelling shaft transmission mechanism is composed of a linear sliding block, a sliding rail, a cylinder, an air swelling shaft transfer rack, a motor, chain wheels and a chain. The tension control system comprises a tension detector, a tension detection roller, a tension controller and the like. The automatic winding device is mainly used for automatically winding plastic films and changing rolls of the plastic films, the effect that winding tension is constant is guaranteed, machines can replace people and thus labor using cost of enterprises can be reduced.