PURPOSE: To stabilize the quality of a film by controlling pressure in a vacuum buffer adjacent to a vacuum processing chamber.

CONSTITUTION: Vacuum processing chambers 3, 4 and vacuum buffers 1, 2, 5, 6 are provided to perform various processes in a vacuum atmosphere. In this case, pressure measuring means 9 in the buffers 5, 6 adjacent to the chamber 4, and pressure regulating means 7, 8 are provided, and its pressure is managed to be controlled. That is, in order to prevent a decrease in the quality of the film due to remaining gas, the remaining gases of the buffers 5, 6 adjacent to the chamber 4 must be checked, but since the analysis of the gas is not simple, the pressure for checking the gas is used to measure the pressure, and conveyed after predetermined pressure is arrived. Thus, a decrease in the quality of the film can be prevented to stabilize the quality of the film.