1. An object detection apparatus that detects an object from an image obtained by taking a picture of a road before a vehicle in the direction of travel, the object detection apparatus comprising: a camera unit that captures and inputs the image of the road before the vehicle; a dictionary modeling the object; a search unit that searches the image with a search window; a histogram production unit that produces a histogram by comparing the image in the search window with the dictionary and counting a detection frequency in a direction parallel to a road plane; and a detection unit that detects the object by detecting a unimodal distribution from the histogram.