In an apparatus for reducing vehicle aerodynamic drag equipped with an air jet device installed at upper and lower positions of a rear of a vehicle and each having a vibrator connected to a diaphragm disposed in an enclosed region and adapted to be driven based on a drive signal to vibrate the diaphragm to jet/suck air through an orifice formed in the region, a vehicle traveling condition is detected, the drive signals for the respective air jet devices are determined independently of each other based on the detected traveling condition, and the vibrators of the respective air jet devices are driven based on the determined drive signals to reduce aerodynamic drag acting on the vehicle.