To provide a gate valve having an upper cover that can be fixed or dismantled by easy work without requiring tightening work of rotating a member.

The gate valve has a valve case which constitutes a part of pipeline, a valve body which displaces between the close position to block the channel in the valve case and the open position which opens this channel, a valve stem 23 which can operate the displacement of the valve body, and a valve cover 25 which rotatably supports the valve stem 23. The valve cover 25 has a bush 16 which is inserted into an opening part on the top face of the valve cover 25 and supports the valve stem 23 from the top face, and an upper cover 17 to cover the bush 16 and block the opening. The bush 16 is engaged to the opening part by a bayonet mechanism. The caulking projection 16c, which is prepared in the bush 16, is inserted into the through hole 17a formed in the upper cover 17, and the upper cover 17 is fixed to the bush 16 by caulking the caulking projection 16c.