Supercharge control apparatus and supercharge control method for supercharged internal combustion engine

A detecting device detects boost condition of each of a plurality of superchargers (19A,19B). The detecting device includes at least two of a pressure ratio detecting unit, which detects the ratio of the pressure downstream each supercharger to the pressure upstream each supercharger; an air flow rate detecting unit, which detects the flow rate of air passing through each supercharger; and a rotational speed detecting unit, which detects the rotational speed of each supercharger. When it is determined that the boost condition of only part of the superchargers (19A,19B) is within the surging area, a control unit increases the air flow rate of the supercharger, the boost condition of which is determined to be in the surging area. Therefore, the limitation of the flow rate of air supply is raised.