To reduce the number of part items and a cost and a ship weight by piping cooling tube group directly inside the tank provided on the lower part of a hull and circulating a medium to be cooled inside the cooling tube group.

A tank 3 in which a seawater is entered by a scoop 2 is provided on the lower part of the hull 1 of a ship. Cooling tube group 4A, 4B are piped directly inside the tank 3 through headers 4a, 4b projected on a tanktop 1a respectively and various kinds of cooling media are circulated inside the cooling tube group 4A, 4B through the piping. Therefore, various kinds of cooling media are thermally exchanged with the seawater directly while concentrating in the tank 3 and cooled. The seawater is introduced into the tank 3 by the scoop 2 while utilizing a ship speed. Therefore, large-scale piping and a pump with a big capacity are dispensed with and by the reduction of the number of parts, a cost is reduced and also a ship weight is reduced.