Abstract: Disclosed is a nighttime road fog detection system. More specifically, the present invention relates to a nighttime road fog detection system which rapidly and accurately detects the time of occurrence of nighttime fog that occurs at dawn before sunrise using open information of closed-circuit television (CCTV) cameras installed on a road and a detection method thereof. According to an embodiment of the present invention, in a mapping image obtained by masking a fog region identified by a fog detection program on an image signal, a region incorrectly determined due to a whitening phenomenon caused by an external light source generated at night is corrected, and thus information about the fog region is more accurately provided.