An auxiliary vacuum chamber 12 according to the invention comprises a container 30 having an opening 10, 14 for taking an object to be processed W into and out of the container. A holder 33a is movably placed in the container 30, which can hold the object W taken therein. The holder 33a can also form a hermetically closed space 32a with a portion of the container 30 when moved in the container 30. The container 30 is provided with supplying means 38a for supplying a gas from the outside of the container 30 into the hermetically closed space 32a. The container 30 is also provided with exhaust means 37 for exhausting the gas from the hermetically closed space 32a to the outside of the container 30. According to the invention, the auxiliary vacuum chamber 12 need not have gate-valves for being opened and shut to the other chambers 4 and 16.