A map image display system comprising: a map data acquisition unit adapted to acquire map data that is divided into a plurality of areas (56, 58) and hierarchically structured into a plurality of layers based on a difference in an amount of road network information; an image display unit adapted to display a map image (51, 57, 59) of a display target area including a road network on a display device based on the map data acquired by the map data acquisition unit; an area division unit adapted to divide the display target area into a plurality of division areas (56, 58) wherein parts of neighboring division areas (56, 58) overlap each other; an image generation unit adapted to generate a map image (51, 57, 59) based on a different layer for each of the division areas (56, 58) generated by the division performed by the area division unit; characterized in that the map image display system further comprises a transmittance change unit adapted to, in an area where neighboring map images (51, 57, 59) generated by the image generation unit overlap, gradually change the transmittance of one of the overlapped map images (51, 57, 59) so that the transmittance of the outside of the division area (56, 58) becomes higher than the transmittance of the inside of the division area (56, 58); and a map image drawing unit adapted to draw the other of the overlapped map images (51, 57, 59) on the display device and, after that, draw the one of the map images (51, 57, 59), whose transmittance has been changed by the transmittance change unit, on the display device with the one of the map images (51, 57, 59) overlapped on the other. a map data acquisition unit adapted to acquire map data that is divided into a plurality of areas (56, 58) and hierarchically structured into a plurality of layers based on a difference in an amount of road network information; an image display unit adapted to display a map image (51, 57, 59) of a display target area including a road network on a display device based on the map data acquired by the map data acquisition unit; an area division unit adapted to divide the display target area into a plurality of division areas (56, 58) wherein parts of neighboring division areas (56, 58) overlap each other; an image generation unit adapted to generate a map image (51, 57, 59) based on a different layer for each of the division areas (56, 58) generated by the division performed by the area division unit; characterized in that the map image display system further comprises a transmittance change unit adapted to, in an area where neighboring map images (51, 57, 59) generated by the image generation unit overlap, gradually change the transmittance of one of the overlapped map images (51, 57, 59) so that the transmittance of the outside of the division area (56, 58) becomes higher than the transmittance of the inside of the division area (56, 58); and a map image drawing unit adapted to draw the other of the overlapped map images (51, 57, 59) on the display device and, after that, draw the one of the map images (51, 57, 59), whose transmittance has been changed by the transmittance change unit, on the display device with the one of the map images (51, 57, 59) overlapped on the other.