The Kanmon Kaikyo Traffic Route is important as an international route, and main route to connect main economic blocks of Japan. In the Kanmon Kaikyo, there is a problem that a route is being buried by sand and clay because of extremely strong tidal current. Therefore, the continuous dredging is needed to keep the route navigable. Kaisho Maru that is an oil recovery ship and a dredger is also dredging the Kanmon Kaikyo with the round-the-clock-system. Then an automatic mooring system was installed on the berth for Kaisho Maru. The automatic mooring system has two movable suckers and fenders to catch the bow and stern side. A hull of Kaisho Maru is absorbed with these suckers, and moored firmly. In order to use this system effectively, Kaisho Maru has to be guided to the positions of suckers correctly. Thus, automatic control system for Kaisho Maru has been developed. Kaisho Maru is controlled by the automatic berthing system with specified point guidance control method. The system guides a reference point on the ship to the specified point on the planned route. In this study, actual berthing data of Kaisho Maru was analyzed and effectiveness of automatic berthing system was evaluated.