1. An object recognizing apparatus, comprising: a viewing direction estimating device that respectively estimates a first viewing direction of a first object captured by a first camera and a second viewing direction of a second object captured by a second camera; a feature extracting device that extracts one or more features respectively from an image containing the first object captured by the first camera and an image containing the second object captured by the second camera; and an object matching device that allocates a weight for each of the one or more features according to the first viewing direction and the second viewing direction, and calculates a similarity between the first object and the second object based on the one or more weighted features, to determine whether the first object and the second object are a same object, wherein: the weight for each of the one or more features reflects a relationship between the first and second viewing directions and effectiveness of the one or more features for object recognition under the first and second viewing directions; the viewing direction estimating device includes: a shooting direction obtaining device that obtains a shooting direction of a camera; a moving direction estimating device that estimates a moving direction of an object based on images captured by the camera; and a viewing angle determining device that determines a viewing direction of the object with respect to the camera according to the moving direction of the object and the shooting direction of the camera; when the moving direction of the object and the shooting direction of the camera are opposite to each other, the viewing angle determining device determines that the viewing direction of the object with respect to the camera is a front viewing direction; when the moving direction of the object and the shooting direction of the camera are the same, the viewing angle determining device determines that the viewing direction of the object with respect to the camera is a back viewing direction; and when the moving direction of the object and the shooting direction of the camera are perpendicular to each other, the viewing angle determining device determines that the viewing direction of the object with respect to the camera is a side viewing direction.