1. An object tracking apparatus for tracking an object included in images provided successively, the object tracking apparatus comprising: at least one non-transitory memory device; at least one processor; a first registering unit configured to register a template generated based on a partial image indicating an object in a predetermined image among the provided images; a first matching unit configured to estimate coordinates of a first object region by performing template matching in which the registered template is compared to another image of the provided images; a second registering unit configured to register a histogram generated based on pixel values of the partial image indicating the object in the predetermined image; a second matching unit configured to estimate coordinates of a second object region by performing histogram matching in which the registered histogram is compared to a histogram of a partial region of the another image; an object region determination unit configured to determine, based on estimation results of the first matching unit and the second matching unit, an estimated object region by employing the estimation results of both the template matching and the histogram matching, wherein, in a case where a distance between the coordinates of the second object region and the coordinates of the first object region is within a predetermined range, the object region determination unit determines the first object region as the estimated object region using the template matching, wherein, in a case where the distance between the coordinates of the second object region and the coordinates of the first object region is not within the predetermined range, the object region determination unit determines the second object region as the estimated object region using the histogram matching, and wherein the first registering unit, the first matching unit, a second registering unit, a second matching unit, and the object region determination unit are implemented by the at least one processor executing at least one program recorded on the at least one non-transitory memory device.