1. An image processing device comprising: a lane marking recognition section that recognizes left and right lane markings from a surroundings image captured by an imaging section; and a leading vehicle recognition section that recognizes a leading vehicle from the surroundings image, the lane marking recognition section determining whether a width direction discrepancy, or a value based on the discrepancy, between a first reference position located between a pair of the left and right lane markings and a second reference position of the leading vehicle is within a predetermined threshold value, and if so, determining that the pair of the left and right lane markings is a true lane marking pair.