A position estimating system capable of accurately estimating the position assumed by a target terminal user based upon measurement of wireless reception signal levels of signals from a target terminal is provided. The position estimating system includes a target terminal that wirelessly transmits a position estimation request, a plurality of reference terminals disposed at specific positions which, measure the signal strength of wireless signals from the target terminal and a position estimating server that estimates the position of the target terminal based upon the reception signal levels measured in correspondence to each of the reference terminals. The reference terminals each include a reception signal level utilization OK/NG judgment unit that makes a judgment as to whether or not the reception signal level value having been measured is to be used in position estimation based upon an index indicating the level of reliability of the reception signal.