A marking line detection system includes an imaging device and an ECU. An information extraction unit of the ECU is configured to extract depth distance information from the imaging device to an imaging object based on image information in an imaging area captured by the imaging device. A road surface area identification unit of the ECU is configured to identify a distant road surface area based on the depth distance information, the distant road surface area being a road surface area that excludes an immediately-preceding road surface area of the vehicle in the image information and is more distant from the vehicle than the immediately-preceding road surface area. A marking line detection unit of the ECU is configured to detect a marking line in the distant road surface area based on image information corresponding to a position of the distant road surface area.