1. A navigation method for providing navigation by using map data, comprising: displaying a menu with which a user specifies an area of a map over which map data are to be updated, the menu containing a map-based option for area specification and a route-based option for area specification, the map data being managed in units of a mesh; displaying a route and a map including the route, and displaying along the route one or more meshes including map data judged to be updated based upon the route, when the route-based option is selected from the options in the menu on display; making a display in which a data update instruction can be inputted; obtaining update data along the route when the data update instruction is input; and executing processing by using the obtained update data.