To provide a light control device which does not make an illumination device die out even when brightness is lowered at outdoors of low temperature.

The light control device comprises a lowest circumferencial temperature estimation part 2 which selects a lowest temperature at midnight from a data depending on the time measured by an annual timer 1 to make it an estimated circumferencial lowest temperature, a light control lowest limit rate setting part 3 which sets a lowest limit rate of light control corresponding to the lowest circumferential temperature at every prescribed time estimated by the lowest circumferential temperature estimation part 2, and a light control part 4 which controls the lighting of the illumination device 5 at midnight depending on the lowest limit rate of light control at every prescribed time set by the light control lowest limit rate setting part 3 when a midnight time is detected from the time measured by the annual timer.