1. An object tracker comprising: a tracking processing unit operative to perform a tracking process of a target object, based on an estimated existence probability distribution of a target object in a first image frame, by defining the candidate contour of a target object in a second image frame, observing the likelihood of the candidate contour by matching against an edge image of the second image frame, and estimating the existence probability distribution of the target object in the second frame, the first image frame and the second image frame forming a moving image in which the target object to be tracked is captured; a target object area detection unit operative to detect the area of the target object in the first image frame by a predetermined analysis method and acquire a predetermined feature amount representing the area; an initial contour estimation unit operative to obtain the estimated existence probability distribution of the target object in the first image frame by temporarily setting at least any one of the values of parameters the tracking processing unit uses for a tracking process and estimate the contour of the target object based on the estimated existence probability distribution; and an initial value determination unit operative to compare the feature amount of the area of the target object based on the contour estimated by the initial contour estimation unit and the feature amount acquired by the target object area detection unit and, when the result of the comparison satisfies a predetermined condition, allows the tracking processing unit to start a tracking process by applying the value of the parameter temporarily set by the initial contour estimation unit.