A gate valve is disposed between first and second chambers and allows a first opening leading to the first chamber and a second opening leading to the second chamber to be communicated and opens and closes. The gate valve includes a valve shaft, first and second valve plates that are attached to a leading end part of the valve shaft, an operation mechanism that moves these valve plates to an evacuation position at which the first opening and the second opening are communicated, a first closed position at which the first opening is closed by the first valve plate, and a second closed position at which the second opening is closed the second valve plate by operating the valve shaft, a fastening mechanism that attaches these valve plates to the valve shaft, and a support mechanism that fasten both end parts of these valve plates in a longitudinal direction.