A gate valve is provided with a main body, and a sealing member which comes into contact with the peripheral edge of a gate when the gate valve is closed. The sealing member includes a protruding first section and a protruding second section which are disposed to extend along the peripheral edge of the main body and protrude from the primary surface when the gate valve is open. A protrusion amount of the first section from the primary surface is greater than a protrusion amount of the second section from the primary surface. The first section is disposed inner to the inner periphery of the primary surface than the second section.