A vehicle comprising: an image display system; an ignition switch; and a camera switch; the image display system comprising: four on-vehicle cameras (1a to 1d) configured to photograph a plurality of images of four directions of surroundings of the vehicle; an image synthesis unit configured to join the plurality of images photographed by the plurality of on-vehicle cameras (1a to 1d) to form a composite image; a mask superposition unit configured to superpose masks on the composite image to cover joints of the plurality of images; a display unit configured to display the composite image having the masks superposed thereon; and a mask control unit configured to detect a predetermined condition, to determine a passage of predetermined time after the predetermined condition is detected, to perform a first display operation of the masks of the composite image only until the passage of predetermined time after the predetermined condition is established, and to perform a second display operation of the masks of the composite image different from the first display operation after the predetermined time, wherein the mask control unit is connected to the ignition switch and to the camera switch of the vehicle and is configured to detect whether the ignition switch is turned ON and to detect whether the camera switch is turned ON, the first display operation is a highlight operation such that the mask displayed by the first display operation is more conspicuous than the mask displayed by the second display operation, and the predetermined condition is that the camera switch is turned ON for the first time after the ignition switch is turned ON. an image display system; an ignition switch; and a camera switch; the image display system comprising: four on-vehicle cameras (1a to 1d) configured to photograph a plurality of images of four directions of surroundings of the vehicle; an image synthesis unit configured to join the plurality of images photographed by the plurality of on-vehicle cameras (1a to 1d) to form a composite image; a mask superposition unit configured to superpose masks on the composite image to cover joints of the plurality of images; a display unit configured to display the composite image having the masks superposed thereon; and a mask control unit configured to detect a predetermined condition, to determine a passage of predetermined time after the predetermined condition is detected, to perform a first display operation of the masks of the composite image only until the passage of predetermined time after the predetermined condition is established, and to perform a second display operation of the masks of the composite image different from the first display operation after the predetermined time, four on-vehicle cameras (1a to 1d) configured to photograph a plurality of images of four directions of surroundings of the vehicle; an image synthesis unit configured to join the plurality of images photographed by the plurality of on-vehicle cameras (1a to 1d) to form a composite image; a mask superposition unit configured to superpose masks on the composite image to cover joints of the plurality of images; a display unit configured to display the composite image having the masks superposed thereon; and a mask control unit configured to detect a predetermined condition, to determine a passage of predetermined time after the predetermined condition is detected, to perform a first display operation of the masks of the composite image only until the passage of predetermined time after the predetermined condition is established, and to perform a second display operation of the masks of the composite image different from the first display operation after the predetermined time, wherein the mask control unit is connected to the ignition switch and to the camera switch of the vehicle and is configured to detect whether the ignition switch is turned ON and to detect whether the camera switch is turned ON, the first display operation is a highlight operation such that the mask displayed by the first display operation is more conspicuous than the mask displayed by the second display operation, and the predetermined condition is that the camera switch is turned ON for the first time after the ignition switch is turned ON.