1. An image feature extraction device comprising: a gradient image calculator generates intensity gradient data with respect to two different directions based on intensity data of image data; a gradient count unit calculates a covariance matrix for each partial area obtained by dividing the image data based on the intensity gradient data; and a feature data output unit calculates two parameters related to a major axis and a minor axis of an ellipse expressed by the covariance matrix, quantizes a range of the logarithms of the parameters for each of the partial area using a predetermined division number, and outputs a feature vector which contains a value only at a dimension corresponding to the quantized range different from the other dimensions.