An object detection apparatus for detecting an object from an image acquired by taking a picture of a road before a vehicle in the direction of travel, the object detection apparatus characterized by comprising: a camera unit for capturing and inputting the image of the road before the vehicle; a storage unit for storing a dictionary classifying the object to be detected with a predetermined resolution, said dictionary being determined to be capable of enabling a detection of the object; the resolution of the dictionary image is determined comprising the following steps: (i) the object detection apparatus produces histograms on dictionary-by-dictionary basis by searching a plurality of sample images containing a detection object with a search window, comparing the sample images in the search window with a plurality of dictionaries of different resolutions, and counting a detection frequency in a direction parallel to a road plane; (ii) lowest resolutions are determined among resolutions of the dictionaries that allow the histograms to have a unimodal distribution and an average resolution value is calculated by averaging the lowest resolutions derived with respect to the plurality of sample images; (iii) the average resolution value is used as a resolution of dictionaries in the object detection process. a search unit for searching the image with a search window; a histogram production unit for producing a histogram by comparing the image in the search window on a pixel basis with the dictionary and counting, for each image row, a detection frequency of the object to be detected in a direction parallel to a road plane, said detection frequency representing a number of comparison results of high similarity between the image and the dictionary image; and a detection unit for detecting whether the histogram has a unimodal distribution, and for detecting the object to be detected from the histogram, if the histogram is detected to have a unimodal distribution. a camera unit for capturing and inputting the image of the road before the vehicle; a storage unit for storing a dictionary classifying the object to be detected with a predetermined resolution, said dictionary being determined to be capable of enabling a detection of the object; the resolution of the dictionary image is determined comprising the following steps: (i) the object detection apparatus produces histograms on dictionary-by-dictionary basis by searching a plurality of sample images containing a detection object with a search window, comparing the sample images in the search window with a plurality of dictionaries of different resolutions, and counting a detection frequency in a direction parallel to a road plane; (ii) lowest resolutions are determined among resolutions of the dictionaries that allow the histograms to have a unimodal distribution and an average resolution value is calculated by averaging the lowest resolutions derived with respect to the plurality of sample images; (iii) the average resolution value is used as a resolution of dictionaries in the object detection process. (i) the object detection apparatus produces histograms on dictionary-by-dictionary basis by searching a plurality of sample images containing a detection object with a search window, comparing the sample images in the search window with a plurality of dictionaries of different resolutions, and counting a detection frequency in a direction parallel to a road plane; (ii) lowest resolutions are determined among resolutions of the dictionaries that allow the histograms to have a unimodal distribution and an average resolution value is calculated by averaging the lowest resolutions derived with respect to the plurality of sample images; (iii) the average resolution value is used as a resolution of dictionaries in the object detection process. a search unit for searching the image with a search window; a histogram production unit for producing a histogram by comparing the image in the search window on a pixel basis with the dictionary and counting, for each image row, a detection frequency of the object to be detected in a direction parallel to a road plane, said detection frequency representing a number of comparison results of high similarity between the image and the dictionary image; and a detection unit for detecting whether the histogram has a unimodal distribution, and for detecting the object to be detected from the histogram, if the histogram is detected to have a unimodal distribution.