A map display system comprising: a map information acquiring unit configured to acquire map information indicating a map to be displayed on a display part; and a congestion level acquiring unit configured to acquire a congestion level for each road section within the map; the map display system being characterized by further comprising a route line display determining unit configured to determine whether a route line is displayed superimposed on any road line; wherein, if a planned travel route from a current position to a destination is being set, the route line display determining unit determines that a route line is displayed superimposed on any road line, the route line representing the planned travel route, each road line representing a road section within the map; and a display controlling unit that, if a route line is displayed superimposed on any road line, displays, based on the map information, the map including the road lines and the route line on the display part and displays congestion lines at a position by a first off-set distance (L 1) far from the road lines on the display part, for all road sections within the map, a congestion line representing a congestion level, the first off-set distance being a distance between a road line and a congestion line by which the route line is not overlapped with the congestion line, if the a route line is not displayed superimposed on any road line, displays, based on the map information, the map including the road lines on the display part and displays the congestion lines at a position by a second off-set distance (L 2) far from the road lines on the display part, the second off-set distance being a distance between a road line and a congestion line by which the road line is not overlapped with the congestion line. a map information acquiring unit configured to acquire map information indicating a map to be displayed on a display part; and a congestion level acquiring unit configured to acquire a congestion level for each road section within the map; the map display system being characterized by further comprising a route line display determining unit configured to determine whether a route line is displayed superimposed on any road line; wherein, if a planned travel route from a current position to a destination is being set, the route line display determining unit determines that a route line is displayed superimposed on any road line, the route line representing the planned travel route, each road line representing a road section within the map; and a display controlling unit that, if a route line is displayed superimposed on any road line, displays, based on the map information, the map including the road lines and the route line on the display part and displays congestion lines at a position by a first off-set distance (L 1) far from the road lines on the display part, for all road sections within the map, a congestion line representing a congestion level, the first off-set distance being a distance between a road line and a congestion line by which the route line is not overlapped with the congestion line, if the a route line is not displayed superimposed on any road line, displays, based on the map information, the map including the road lines on the display part and displays the congestion lines at a position by a second off-set distance (L 2) far from the road lines on the display part, the second off-set distance being a distance between a road line and a congestion line by which the road line is not overlapped with the congestion line.