A navigation system in which a mobile terminal side
is not equipped with a CD-ROM for storing map database
, but implements an on-demand navigation function by sharing the one provided within a server
. By limiting the communications between the mobile terminal
and the server
only to the beginning of the route guidance and the moment at which the mobile terminal has deviated from the route, the communication traffic can be reduced, minimizing thereby the communication cost and the total power consumption as a whole, and further even when the mobile terminal
has deviated from the guide route, the system can readily provide the user with information by which he can reach his destination through communications with the server, and enabling also an indication of the name of the road to be taken at every crossings.