A time difference information supply system includes a terminal unit for receiving satellite signals and a plurality of communication base stations asynchronous with one another, which communicate with the terminal unit. The terminal unit includes distance information storing means for storing distance information, satellite time synchronizing means for maintaining synchronicity with time of the positioning satellites, transmission radio wave receiving means for receiving the transmission radio waves from the plural communication base stations simultaneously or sequentially, reception time information producing means for producing reception time information, communication base station distance acquiring means for acquiring distances between the terminal unit and the communication base stations, estimated reception time information producing means for producing estimated reception time information, transmission time difference information producing means for producing transmission time difference information.