A carton forming device is composed of a connecting rod driving slider mechanism, a gear-rack stroke doubling mechanism and an absorbing arm assembly. The connecting rod driving slider mechanism is composed of a rocker arm, a connecting rod, a joint bearing, a slider and a guide shaft. The carton forming device has the advantages of reasonable structure, simplicity in operation, stability in running, accuracy in control, high efficiency, low cost, stability and reliability, and the like. Carbon forming is realized by enabling an absorbing arm on one side to be under pressure, a carbon is obliquely erected in a hopper, and the carbon is formed in the process when the absorbing arm absorbs the carbon out of the hopper to a cigarette pile to-be-boxed workstation. A rocker arm-connecting rod mechanism is adopted, and the carbon is driven to be in linear motion through the slider. Especially, due to adoption of gear-rack transmission, action stroke of the absorbing arm is increased, and effect of small size, stability and reliability, simple action and the like of the device is realized. Troublesome mechanism adjusting during forming of carbons different in specification and size is avoided, the problem that an existing carbon forming device is complex in process, poor in stability, low in efficiency and the like is solved, and the carton forming device is an ideal supporting device special for cigarette packaging carbon forming.