The present invention easily evaluates the positioning accuracy by using fewer signal sources. The receiver is a positioning system for estimating the position of the receiver itself which is constituted by: a distance calculation section which calculates information indicating the respective distances between a plurality of GPS satellites and the receiver on the basis of signals which are transmitted by the plurality of GPS satellites and received by the receiver; a position calculation section which calculates the position of the receiver from information indicating the positions of the respective GPS satellites and information indicating the respective distances thus calculated; a distance difference calculation section which calculates, for each of the GPS satellites, the differences between the respective distances from the calculated position of the receiver to the respective GPS satellites, and the respective distances calculated by the distance calculation section; and a position accuracy evaluation section which evaluates an accuracy of the calculated position of the receiver on the basis of variation, between the GPS satellites, of the calculated differences, for each of the GPS satellites.