A basic EGR flow rate calculation part calculates a basic EGR flow rate based on an intake manifold pressure, which is a pressure in an intake manifold, an exhaust pressure, which is a pressure in an exhaust pipe, an exhaust temperature, which is a temperature in the exhaust pipe, and an opening degree of an EGR valve. An EGR flow rate correction part corrects the basic EGR flow rate based on an intake manifold pressure ratio, which is a ratio between the intake manifold pressure and the exhaust pressure, and an exhaust VVT phase angle of an exhaust VVT mechanism, to thereby calculate a corrected EGR flow rate as an EGR flow rate.