An external active air flap apparatus of a vehicle is provided The external active air flap apparatus removes the gap between the air flaps disposed vertically after sealing an air passage of a radiator grill by the air flaps and minimizes the gap between the air flaps and the radiator grill, thereby improving aerodynamic performance of the vehicle. The external active air flap apparatus includes an air flap positioned at a rear of a radiator grill that rotates to open and close an air passage of the radiator grill. Further, a flap fixing mechanism is mounted on the radiator grill and the air flap contracts the air flap with the radiator grill by applying a wind pressure to the air flap operated to seal the air passage.