PURPOSE: To reduce wind pressure resistance so as to reduce hull resistance by forming hollow structure bodies at the front face of the upper structure of a marine vessel, and forming the lower end of each hollow structure body into an air suction port and the upper end into an air discharge port so as to let wind pressure hitting against the front face of the user structure flow smoothly upward.

CONSTITUTION: Semi-cylinder bodies 4 are vertically fitted to the front wall 3a of an upper structure 3 on the upper deck 2 of a marine vessel 1 to form hollow structure bodies 5. The lower end opening part of each hollow structure body 5 is formed into an air suction port 5a, and the upper end opening part is formed into an air discharge port 5b. A wind B blowing against the lower part of the front wall 3a of the upper structure by the sailing of the marine vessel 1 is sucked from the air suction ports 5a at the lower ends of the hollow structure bodies 5, and the sucked wind B is blown up toward the air discharge ports 5b by the chimney effect so as to flow smoothly upward. The front face pressure of the front wall 3a is thereby reduced, so that hull resistance is reduced.