A method and apparatus for exhausting gas from a coating material. The coating material is fed in the bottom part area of a drum (3) rotating around an essentially vertical axis inside a vacuum tank (1), whereby the rotating motion of the drum causes the coating material to rise up the inner wall of the drum and to discharge from the upper edge of the drum as a thin film against the inner wall of a vacuum tank, wherefrom the coating material flows downwards. The coating material is arranged to rise up the wall of the drum stepwise, so that the coating material will form a thin veil-like film on at least two different step levels (10-12), whereupon the gas bubbles in the coating material will break and be discharged from the coating material.