1. An information processing device, comprising: outline extraction means for extracting an outline of a subject within a picked-up image; characteristic amount extraction means for generating first characteristic amounts corresponding to sample points extracted from the outline of the subject; estimation means for estimating a posture the subject, the estimation means being configured to: calculate matching costs indicative of a difference between the first characteristic amounts and second characteristic amounts that are prepared in advance and represent predetermined postures different from each other; and identify one of the predetermined postures as the estimated posture, based on the matching costs; and determination means for determining an accuracy of the estimated posture based on at least one corresponding matching cost, when the estimation means carries out the estimation.