1. A preceding-vehicle identifying apparatus for identifying, as a preceding vehicle, a vehicle running ahead of an own vehicle based on an own-vehicle lane probability which is a probability that the vehicle is running in the same lane as an own-vehicle lane in which the own vehicle is running, comprising: a detection signal acquiring section that receives at least two of a first detection signal indicative of a curvature of a curved road ahead of the own vehicle, a second detection signal indicative of a track of a vehicle running ahead of the own vehicle and a third detection signal indicative of the own vehicle' having entered the curved road, the first to third detection signals being outputted from first to third detecting sections, respectively, which are mounted on the own vehicle; a first calculating section that calculates at least two of a first probability of existence of the curved road ahead of the own vehicle based on the first detection signal, a second probability of existence of the curved road ahead of the own vehicle based on the second detection signal and a third detection signal of existence of the curved road ahead of the own vehicle based on the third detection signal, and calculates an integrated probability of existence of the curved road ahead of the own vehicle based on integration of the at least two of the first to third probabilities; and a second calculating section that calculates the own-vehicle lane probability based on a distance between a predicted running line of the own vehicle along which the own vehicle is predicted to run and the track of the vehicle running ahead of the own vehicle, and performs an own-vehicle lane probability compensation process for compensating the calculated own-vehicle lane probability based on the integrated probability.