To provide a water non-cut-off installation method for a sluice gate, by which installation under a water non-cut-off state is enabled.

When the sluice gate A with a door stop 3 mounted on a wall body F through a foundation G and a door body 4 fitted into the door stop 3 in a freely vertically movable manner is secured in a water way, (1) a process, in which the door body 4 is brought to a totally enclosed state, an opening, in which water is passed, is formed between the wall body F and the door stop 3 and the sluice gate A is positioned and adjusted and the sluice gate A is fixed by a gate fixing bolt 13 and a nut 16 set up on the wall body F side, and (2) a process, in which the door body 4 is brought to an open state and underwater mortar is placed between the wall body F and the door stop 3 as the foundation, are conducted in the order.