An activation control apparatus controls activation of an airbag unit. An electronic control unit detects a floor deceleration Gf and front decelerations GI, Gr from signals output from a floor sensor and front sensors. Also, the electronic control unit calculates a velocity change Vn from the floor deceleration Gf, and determines the severity of a collision. Further, the electronic control unit determines the state of a symmetric flag FRG through comparison between the front decelerations GI, Gr and the value of a front determination map boundary, serving as a front threshold variation pattern and through comparison between the floor deceleration Gf and the value of a low or high map boundary, serving as an activation threshold variation pattern. Then, on the basis of results of the severity determination and the state of the symmetric flag FRG, the electronic control unit determines a delay time in relation to the activation of the airbag unit. An airbag is expanded and deployed on the basis of the delay time.