A wastegate is provided in an exhaust bypass passage that allows exhaust gas to bypass a turbine wheel of an exhaust turbine-type forced-induction device. A required boost pressure is set in accordance with a running state of an engine. A controller is configured to control a drive force of the wastegate to a magnitude that achieves the required boost pressure when the required boost pressure is higher than a preset pressure, and control the drive force to a magnitude that achieves a higher boost pressure than the required boost pressure when the required boost pressure is less than or equal to the preset pressure.