An evacuating valve includes a chamber port structure to be connected to a vacuum vessel in which a plasma is produce to create a plasma atmosphere, a pump port structure to be connected to a vacuum pump; a valve casing defining a passage connecting the chamber port structure and the pump port structure, and a valve mechanism for opening and closing the chamber port structure. At least two expended parts are formed by expanding an end part of the inside surface of the chamber port structure, and the valve element has a large part capable of being pressed against the valve seat with the sealing member held between the large part and the valve seat, and at least two small parts capable of being fitted in the expanded parts of the chamber port structure.