A car navigation system including route judgment means for judging whether an input place name is suitable for a route extending to a destination, and judgment result output means for outputting a judgment result, so that a car can be guided and navigated along a suitable route extending to the destination by inputting a place name written on a road sign or the like. The judgment result is output with a voice message or image display. When plural place names are input, the judgment is made on each of the place names, and the most suitable place name is selected and output.