A deflector apparatus for regulating air flows at a rear of a vehicle includes a movable portion arranged at a rear of a roof panel and an upper of a rear window of a vehicle and extended in a vehicle width direction. The movable portion is movable to increase and decrease a protrusion amount of a front end portion of the movable portion in a vehicle front-rear direction from an upper surface of the roof panel to upward. The deflector apparatus further includes a driving system for driving the movable portion to decrease (increase) the protrusion amount as a vehicle speed increases (decreases) to decrease (increase) an amount of air introduced by the movable portion and flowing along the rear window.