COLLISION AVOIDANCE SYSTEM AND COLLISION AVOIDANCE METHOD

A collision avoidance system (1) is provided with: a rear detection device (30) arranged in a host vehicle (10) and capable of detecting an object directly behind the host vehicle, an object to the rear-right of the host vehicle, and an object to the rear-left of the host vehicle in a non-contact manner; a computation processing unit (51) that outputs, on the basis of a detection result from the rear detection device, the presence/absence of the possibility of a collision between the host vehicle and a first following vehicle approaching the host vehicle from directly behind, the presence/absence of the possibility of a collision between the host vehicle and a second following vehicle approaching the host vehicle from the rear-right, and the presence/absence of the possibility of a collision between the host vehicle and a third following vehicle approaching the host vehicle from the rear-left; and a warning device (7) that generates, on the basis of an output result from the computation processing unit, a first warning when there is the possibility of a collision with the first following vehicle, a second warning when there is the possibility of a collision with the second following vehicle, and a third warning when there is the possibility of a collision with the third following vehicle.