The invention discloses a pressing device for a folding part on the top of a corrugated case. The pressing device comprises a pressing frame. The pressing frame comprises a vertical supporting plate. The vertical supporting plate is located on one side of the middle of a conveying belt. A vertical sliding groove is formed in the middle of the vertical supporting plate. Two connecting adjusting plates are fixed to the outer side wall of the vertical supporting plate. The two connecting adjusting plates are located at the upper end and the lower end of the vertical sliding groove. A lifting drive motor is fixed to the outer wall of the lower portion of the vertical supporting plate. The two ends of an adjusting screw are hinged to the two connecting adjusting plates. An output shaft of the lifting drive motor is connected with one end, stretching of the connecting adjusting plate at the lower portion, of the adjusting screw rod through a coupler,. A lifting plate is inserted in and sleeved with the vertical sliding groove and is in screw joint in the adjusting screw rod. The lifting plate is located above the conveying belt. The pressing device can be used for bending and compacting an upper overturning part after first time of bending, and the pressing device is good in effect and good in bending effect.