To facilitate installation or increase of fish bank with respect to a method for increasing a fish bank.

A guide rope 5 is connected to a floating buoy 3 and an anchor 4. A stationary fish bank unit 1 is moved on a guide rope 5 connected to the floating buoy 3 and sunk in the sea. Consequently the stationary fish bank unit 1 is sunk by using the guide rope 5 as a guide in the direction of the anchor 4. The lower side of the stationary fish bank unit 1 has a recess so that the upper part of another stationary fish bank unit 1 bites into the recess and a plurality of the stationary fish bank units 1 are mutually connected under water.