Gate valve

A gate valve comprising:

• a valve box comprising:
• a hollow portion;
• a first opening portion and a second opening portion that are provided so as to sandwich the hollow portion;
• an inner surface formed around the first opening portion;
• and a flow passage passing through the hollow portion, the first opening portion, and the second opening portion;
• a support body disposed inside the hollow portion;
• a valve plate comprising:
• a fixed valving section that is securely fixed to the support body and has a first outer-peripheral face which is located on an outer side in a radial direction of the fixed valving section;
• a movable valving section disposed so as to surround the first outer-peripheral face of the fixed valving section;
• a first peripheral region;
• and a second peripheral region, the movable valving section sliding in a direction in which the flow passage is extended, the movable valving section comprising a first seal portion which is in contact with the inner surface and is pressed onto the inner surface;
• a first biasing section disposed at the first peripheral region, allowing the movable valving section to move toward the first opening portion, allowing the movable valving section to come into contact with the inner surface, pressing the movable valving section onto the inner surface, and closing the flow passage, the first biasing section being an elastic element provided directly below the first seal portion in the movable valving section;
• and
• a second biasing section disposed at the second peripheral region, allowing the movable valving section to move toward the second opening portion, and releasing the flow passage by separating the movable valving section from the inner surface.