PURPOSE: A floating roof device is provided to prevent increase of actual vapor pressure by reducing a gas-liquid contact surface while suppressing a sloshing phenomenon in a tank. CONSTITUTION: A floating roof device comprises a floating body(110) and a blocking part(120). The floating body is floated on the surface of fluid stored in a tank. The blocking part is installed on the top of the floating body to block the contact of fluid in the tank and gas. The floating body has a hemisphere shape. The inside of the floating body is formed into a hollow shape and multiple perforated parts are formed on the surface of the floating body.
