1. A map display apparatus which displays a three-dimensional map on a screen, based on map data including data regarding a three-dimensional object, wherein the map data includes a display correction flag indicating whether or not to execute a correction so that a line of the three-dimensional object in vertical direction should be vertical, when the three-dimensional object is displayed on the screen, and the map display apparatus comprises a correction unit operable to execute a correction, in the case where the display correction flag indicates that the correction should be executed, so that the line of the three-dimensional object in vertical direction should be vertical when the three-dimensional object is displayed on the screen.