A navigation device and a traffic line display method which make a user reliably recognize the relationships between traffic lines and roads when the traffic lines are displayed so as to correspond to the roads which are positioned near one another in a concentrated manner or connected to one another are provided. When the roads currently displayed include roads which belong to a certain road type and which are positioned near one another within a predetermined distance or connected to one another and when at least one of the roads has heavy traffic, the vicinity/connection roads positioned near one another within a predetermined distance or connected to one another and the corresponding traffic lines are clearly distinguished from one another by displaying the roads and the corresponding traffic lines so as to be visually separate from one another. Accordingly, the relationships between the traffic lines and roads are reliably recognized.