A pendulum gate valve incorporates an improved power transmission device for transmitting the movement of a pivot arm of the valve to a valve disk that selectively closes the valve. The power transmission device has a supporting plate and a valve disk support that is fixed to a tip end of the pivot arm and movable relative to the valve disk. First and second facing roller guide grooves, formed on the valve disk and on the valve disk support, respectively, extend obliquely downwardly so as to be separated from the valve disk. Third and fourth facing roller guide grooves, formed on the valve disk support and the supporting plate, respectively, extend obliquely downwardly so as to approach the valve disk. A first roller engages the first and second roller guide grooves, and a second roller engages the third and fourth roller guide grooves.

A gate valve including a valve disc for opening and closing an opening formed in a partition wall for separating a processing chamber from an other chamber, a valve seat formed on the wall around the opening, and a block provided on a side surface of the valve disc facing the processing chamber for filling up the opening. The valve disc is moved selectively brought into contact with the valve seat. When the opening is closed by the valve disc the block is positioned in the opening to close the opening, and when the opening is not closed by the valve disc the block is not positioned in the opening. A gate valve includes a valve disc for opening and closing one side of an opening formed in a partition wall for separating a processing chamber from an other chamber, a valve seat formed on one side surface of the wall around the opening, a closing member for opening and closing the other side of the opening, and a groove formed in the wall for receiving therein the closing member. The valve disc and the closing member are moved selectively to a position where the valve disc is brought into contact with the valve seat and the closing member is positioned in the opening at the other side surface of the wall facing the processing chamber to close the opening, and a position where the valve disc is separated from the valve seat and the closing member is inserted into the groove.