An ECU alternatively changes a target air-fuel ratio At to a rich side and a lean side by active air-fuel ratio control. The ECU measures an oxygen storage capacity OSC of an exhaust purification catalyst based on an oscillation period of the target air-fuel ratio At and the target aft-fuel ratio At, and executes a deterioration determination with respect to the exhaust purification catalyst based on the measurement value. When executing the deterioration determination, the ECU closes a waste gate valve to prevent a decrease in the accuracy of the deterioration determination that is caused by two kinds of exhaust gas whose flow paths are different from each other arriving at the area surrounding an air-fuel ratio sensor.