1. An image recognition device comprising: an image acquirer configured to acquire a primal image; and an object recognizer configured: to calculate gradient magnitude images of the primal image for plural directions, to scan the gradient magnitude images with a window which calculates rectangular feature values within the window, and to recognize a target object using a classifier using at least two of the rectangular feature values; wherein at least one of the rectangular feature values is calculated based on intensity values in at least two of a first type of rectangular areas on one of the gradient magnitude images; at least one of the rectangular feature values is calculated based on intensity values in at least two of a second type of rectangular areas on at least two of the gradient magnitude images acquired for different gradient directions of the plural directions; and one of the at least two of the second type of rectangular areas is placed on one of the at least two of the gradient magnitude images, while another of the at least two of the second type of rectangular areas is placed on another of the at least two of the gradient magnitude images.