A positioning system capable of reducing the volume of data communication in a server positioning system is provided. A terminal device has the information for a positioning transmitting section and can transmit information for positioning containing the actually measured current positioning basic information and/or the estimated basic information to the positioning device. The amount of the estimated basic information is smaller than the amount of the current positioning basic information, thus, the amount of information that the terminal device transmits to the positioning device becomes smaller in the case where the terminal device transmits the estimated basic information with respect to the position information satellite having the difference within the allowable range compared to the case where it transmits only the actually measured current positioning basic information with respect to all of the position information satellites.