An estimated time-to-collision (TTC) calculation apparatus includes a distance acquisition unit, relative velocity acquisition unit, relative acceleration acquisition unit, and estimated TTC calculation unit. The distance acquisition unit acquires a distance X between the own vehicle and an object. The relative velocity acquisition unit acquires a relative velocity V of the object with respect to the own vehicle. The relative acceleration acquisition unit acquires a relative acceleration β of the object with respect to the own vehicle. The estimated TTC calculation unit calculates an estimated TTC t until the own vehicle collides with the object. In this apparatus and method, the estimated TTC calculation unit calculates t, based on the distance X and the relative velocity V, when the own vehicle is accelerating, and when the own vehicle is decelerating, calculates t based on the distance X, the relative velocity V, and the relative acceleration β.