A mobile terminal which has a positioning function, a positioning method and a positioning system for implementing positioning with plural processes and selecting an optimum process by which positioning can be executed with the least error in positioning accuracy. A positioning method applied to a mobile terminal which is provided with a positioning function, wherein a positioning result is obtained by selectively using a first calculation process for finding out a weighted average value from the results of two or more latest positioning calculations each time a measurement has been made based on the results of a plurality of positioning calculations, and a second calculation process for finding out a weighted average value by adding the latest positioning result as a calculation factor to the weighted average of past positioning results each time a measurement has been made based on the results of a plurality of positioning calculations.