1. A feature vector extraction device comprising: a processor that sets a plurality of cells each representing a position and range for counting a feature vector of a target on the basis of a plurality of images containing a target for learning use, wherein the target is a multi-jointed body and wherein the processor is configured to: select two feature points from among three or more feature points which are set in the image and represent the target for learning use, and normalize a size and direction of each of the feature points, calculate a mean position and a variation from the mean position for each of other feature points than the selected two feature points of the normalized feature points, decide a position of each of the cells on the basis of the mean position and decide a size of the each of the cells on the basis of the variation, count the feature vector based on the position and the size of each of the cells; generate a histogram obtained by counting the feature vector for each of the cells; and use the histogram to recognize the target.