A gate valve includes: a valve box; a support body disposed inside a hollow portion; a valve plate including a fixed valving section, a movable valving section sliding in a direction in which a flow passage is extended, a first peripheral region; and a second peripheral region; a first biasing section disposed at the first peripheral region, allowing the movable valving section to move toward a first opening portion, allowing the movable valving section to come into contact with an inner surface, pressing the movable valving section onto the inner surface, and closing the flow passage; and a second biasing section disposed at the second peripheral region, allowing the movable valving section to move toward a second opening portion, and releasing the flow passage by separating the movable valving section from the inner surface.