PURPOSE: To obtain a pressure control device for a projection picture tube, which can prevent a contact of coolant with air and which can prevent intrusion of dust or the like coming out of a narrow tube in the coolant.

CONSTITUTION: A narrow tube 7 is fitted to a liquid container 3 for combining a cathode ray tube 1 with a projection lens at a constant distance. A sealing material 10 for preventing direct contact of the outside air with the coolant 5 flats on the liquid surface of the coolant 5 halfway the narrow tube 7.