To provide a gate valve of simple configuration easily correctable in the opening side space of a valve box valve seat to achieve excellent barrier property.

The gate valve includes a valve box having an opening and a metal valve box valve seat; a valve element mounted to a valve stem and having a metal valve element valve seat; and a lid that blocks the opening of the valve box and allows the valve stem to be inserted through. The valve element valve seat is formed in wedge shape, and the valve box valve seat is formed in inverted truncated chevron shape. One or both of the valve box opening and the lid are provided with correcting means for correcting the thickness direction strain of the valve element from the outside. In this gate valve, the space of the valve box valve seat can be easily corrected to achieve excellent barrier property with simple configuration.