To make the locking and unlocking more easily gate door bodies for a boat and also safely and quickly pass the boat through the gate at a low cost without using electric device and without manually operating the door body by seamen stretching their bodies from the deck of the boat after stopping the boat before passing the gate thereby eliminating the previous problems and improving the conventional operation.

A force pushing the door bodies 2 and 3 by the boat is interlocked to a lock device of the door bodies through a crank mechanism for unlocking and opening doors and, after passage of the boat, the door is closed and locked automatically with no operation, thereby realizing a low cost, free maintenance, and passage of the boat safely and quickly by the opening, closing and locking devices for the gates for plying the boat.