1. An apparatus for recognizing a vehicle travelling behind comprising: a detector for detecting images of objects existing behind a first vehicle in which the apparatus is installed to obtain distance data on the objects in relation to the first vehicle, thus recognizing one of the objects as a second vehicle travelling behind the first vehicle based on the distance data; a first determining unit for determining the type of the second vehicle in size based on the images; and a second determining unit for determining whether the second vehicle is an emergency vehicle based on the images.