An intake air control apparatus of an engine includes a housing having an intake air inflow passage for receiving external air, an exhaust gas inflow passage for receiving recirculated exhaust gas, and an intake air supply passage for supplying the external air from the intake air inflow passage or the exhaust gas from the exhaust gas inflow passage to the engine. A motor gear rotates together with an output shaft of the motor. A connection gear is engaged and rotates together with the motor gear. A recirculation gear is engaged and rotates together with the connection gear. A recirculation valve opens and closes the exhaust gas inflow passage since the recirculation valve rotates together with the recirculation gear. An intake air gear is engaged and rotates together with the connection gear. An intake air throttle valve opens and closes the intake air inflow passage.