The invention discloses a packaging machine and belongs to the field of packaging machinery. The packaging machine comprises a front rack, a rear rack and an opening and closing mechanism. The upper portion of the front rack is hinged to the upper portion of the rear rack. A piece to be opened is rotationally connected with a fixed piece. The opening and closing mechanism comprises a screw mechanism, a drive mechanism, a first base and a second base. The screw mechanism comprises a threaded shaft and a threaded cylinder, wherein the axis of the threaded shaft coincides with the axis of the threaded cylinder, the threaded shaft and the threaded cylinder are in threaded connection and can rotate relative to each other, the threaded shaft is in transmission connection with the drive mechanism, the drive mechanism is hinged to the first base, and the threaded cylinder is hinged to the second base. The opening and closing mechanism is simple in structure and convenient to maintain. The packaging machine comprises the front rack, the rear rack and the opening and closing mechanism. The upper portion of the front rack is hinged to the upper portion of the rear rack, the first base is connected with the front rack, and the second base is fixedly connected with the rear rack. After the packaging machine adopts the opening and closing mechanism, the structure of the packaging machine becomes simple, maintaining is very convenient, and locking can be reliably carried out.