1. An image processing apparatus comprising: object detecting means for detecting each object of a plurality of objects contained in a plurality of images arrayed in order of points in time at which said images are taken, respectively; tracking means for tracking an object by connecting two objects which are respectively detected from two images taken at different points in time among said plurality of images and which can be considered to be a same object; associating means for associating said plurality of objects with each other based on a result of tracking objects by said tracking means; evaluating means for giving evaluations to said each object detected with said object detecting means, respectively; and association evaluating means for giving an evaluation to another object which has been associated by said associating means with the object to which the evaluation has been given by said evaluating means, based on the evaluations made by said evaluating means, wherein said associating means executes association when one or more of the following conditions occur including a condition of associating objects in a case in which said objects are coupled into one object, a condition of associating objects in a case in which one object is separated into said objects, and a condition of associating objects in a case in which distances among said objects become shorter than a predetermined threshold value.