Gas cap device for screen printing machine and screen printing machine

The invention discloses a pneumatic jacking device for a screen printing machine and the screen printing machine. The pneumatic jacking device comprises a base and a mounting frame, and further comprises a positioning assembly and a clamping assembly which are arranged on the mounting frame; the positioning assembly comprises a suction cup, a positioning head, a communicating mechanism and an air bag sleeve, the positioning head is matched with the glass cup and installed on the installation frame, the suction cup is arranged at one end of the positioning head, and the positioning head is sleeved with the air bag sleeve; when the suction cup is extruded, air in the suction cup enters the air bag sleeve through the communicating mechanism, so that the air bag sleeve expands to extrude and position the inner wall of the glass cup. The inner wall of the glass cup is extruded and positioned through expansion of the inflated air bag sleeve, and the air bag sleeve can deform greatly, so that the device can adapt to