A pit gate includes a gate body which is inserted between a pool portion storing water and a canal portion connected to the pool portion and is configured to change a flow state of the water, and a seal portion (6) which is accommodated in a groove-shaped accommodation recess formed in the gate body and seals between the pool portion and the gate body. The seal portion (6) includes a low-rigidity portion (10) which is relatively easily deformed by a load according to a water pressure from the pool portion side, and a high-rigidity portion (11) which is provided on the pool portion side of the low-rigidity portion and is not easily deformed relatively by the load.