1. A background generation apparatus for generating a background by removing a moving object from an input image acquired by means of an image processing unit, the apparatus comprising: a feature vector extractor for extracting predetermined features at arbitrary positions in the input image to calculate input feature vectors; an average processor for calculating an average of the input feature vectors, calculating base feature vectors in which the outliers contained in the input image are suppressed, and generating a base image composed of the base feature vectors; a data accumulator for accumulating the base feature vectors or the base image; and a statistical processor for estimating the central value from the sequence data representing the base feature vectors for arbitrary positions in the input image and accumulated in the data accumulator, and calculating the background feature vectors to generate the background composed of the background feature vectors.