PURPOSE: An anti-sloshing device is provided to suppress sloshing in the outside of a liquid cargo storage tank by increasing rigidity at the edge of the anti-sloshing device which is positioned in the outside of the liquid cargo storage tank. CONSTITUTION: An anti-sloshing device comprises multiple buoyancy units(10) and fastening members. The buoyancy units float on liquid cargo stored in a liquid cargo storage tank. The fastening members connect the buoyancy units with each other. The buoyancy units are connected to the outside of the liquid cargo storage tank in multiple layers.
