PURPOSE: To improve the precision of feedback control over a wide operational region by selecting operational regions where a variable tongue section changing the exhaust gas quantity or an exhaust bypass valve is used for control and performing the respective control only in the predetermined operational region.

CONSTITUTION: In an operational region where control is performed via a variable-capacity means 7, only the first control quantity calculating means 3 calculates the control quantity in response to the deviation between the target supercharged air pressure and the detected supercharged air pressure, and the supercharged air pressure is controlled via the variable-capacity means 7. In an operational region where control is performed via an exhaust bypass valve 8, only the second control quantity calculating means 4 calculates the control quantity in response to the said deviation, and the supercharged air pressure is controlled via the exhaust bypass valve 8. Multiple control means controlling the supercharged air pressure perform independent feedback control in the predetermined regions respectively and the control regions are not overlapped, thus no interference is given even if multiple regions are used for control.