Boost pressure controller for internal combustion engine

A boost pressure controller for an internal combustion engine provided with a low-pressure and a high-pressure EGR devices and capable of obtaining boost pressure suitable for a ratio between the amounts of exhaust gases recirculated by the low-pressure and high-pressure EGR devices, thereby making it possible to ensure excellent drivability. The boost pressure controller controls the boost pressure based on the opening of a boost pressure control valve, set according to detected operating conditions of the engine. A lower limit value for limiting the opening of the boost pressure control valve is set, and a ratio parameter indicative of a ratio of an amount of exhaust gases recirculated by the low-pressure EGR device to an amount of exhaust gases recirculated by the high-pressure EGR device is calculated. The lower limit value is corrected such that it is increased as the ratio parameter is larger.