The invention discloses a carton opening device, and belongs to the field of carton processing equipment. A feeding sliding plate is fixed above a base, an air pressure cylinder is vertically positioned right above a conveying belt, the carton opening device is installed at the bottom of an air pressure cylinder main shaft, a discharging sliding plate is fixed at the top of a third support, a first motor is fixed at the right end of a motor base, the conveying belt is wound between a first roller and a second roller, a controller is installed in front of the motor base, a positive displacementdevice is fixed below the conveying belt, a second motor is fixed at the left end of the motor base, and a second ultrasonic sensor is fixed above the carton opening device. According to the carton opening device, the conveying belt drives the carton to advance, the height and position information of the carton are detected through the ultrasonic sensor, the direction of the carton adhesive tapewhich is corrected by a positive position device is consistent with the advancing direction of the conveying belt, the carton opening device is used for cutting off the adhesive tape around the cartonto finish the carton opening operation, so that the manual labor is reduced, and the production efficiency is improved.