PURPOSE: To keep the contact position of the outer plate of a boat with the roller fender at a certain position regardless of time tidal ebb and flow, by fitting shaking-out type roller fenders as mooring means on a floating structure.

CONSTITUTION: A boat 1 is moored between a pair of floating structures 2, 2 by shaking-out type roller fender 4 attached to the floating structure 2. And the floating structures 2 are moored to be vertically movable in accordance with the tidal ebb and flow, while the horizontal movement being restricted through mooring dolphine 5 fixed on the sea bottom. In this way, the contact position of the roller fenders 4 with the outer plates of the boat 1 can be kept at a constant position regardless of the tidal ebb and flow.