1. A method for detecting a pedestrian based on a far infrared ray (IR) camera at night, the method comprising: receiving a thermal image of a pedestrian; obtaining a first response value at each pixel of the thermal image using a difference of Gaussian (DoG) filter; measuring a variance value at each pixel of the thermal image; creating a binary image by binarizing a second response value at a pixel calculated through a multiplication of the first response value and the variance value; creating a pedestrian candidate cluster from the binary image using a component labeling method; detecting the pedestrian by classifying the pedestrian candidate cluster using at least one classifier learned based on a behavioral characteristic of the pedestrian; and calculating a position of the pedestrian.