A vehicle tunnel detecting device includes an image pickup unit for picking up images of a forward area and an obliquely upper area with respect to a travel direction of a vehicle, an obliquely upper area brightness reduction detecting unit for judging whether an average brightness of the images of the obliquely upper area with respect to the travel direction picked up by the image pickup unit is lower than a predetermined value, a brightness difference detecting unit for calculating a difference in average brightness between the images of the forward and obliquely upper areas achieved by the image pickup unit when it is judged by the obliquely upper area brightness reduction detecting unit that the average brightness of the image of the obliquely upper area is lower than the predetermined value, and a tunnel identifying unit for identifying a tunnel when the difference in average brightness between the image of the forward area and the image of the obliquely upper area that is calculated by the brightness difference detecting unit is lower than a predetermined value.