To display a message indicating the replacement of the back light on a screen when the life of the back light canes to the end.

This display device compares the use time of the back lights with a previously set maximum use time of the back lights, indicates the replacement of the back lights 107 and 108 and resets the use time of the back lights when the use time of the back lights exceeds the maximum use time, and counts and stores the use time continuously in a storage part 102 and displays the use time of the back lights at the point of time of the storage on the screen.