There is provided a controller, for a supercharger-equipped internal combustion engine, that can accurately estimate a supercharging pressure, without providing a pressure sensor for detecting the supercharging pressure. In a controller for a supercharger-equipped internal combustion engine, a correction value for correcting a supercharging pressure estimation value is changed so that an effective opening area estimation value, estimated based on a supercharging pressure estimation value and the like, approaches a preliminarily set effective opening area default value corresponding to a throttle opening degree detection value.