To provide an obstacle detection system capable of preventing the start of an obstacle avoidance operation from being delayed in a following vehicle even when an obstacle such as a pedestrian and a bicycle is detected by a forward vehicle.

This obstacle detection system comprises imaging devices 1 and 2 imaging the outside of a vehicle, an image processing device 3 acquiring image data photographed by the imaging devices 1 and 2, applying image recognizing treatment thereto, and detecting for the presence or absence of an obstacle based on the results of the treatment, and an output device outputting information on the presence or absence of the obstacle detected by the image processing device 3. The image processing device 3 determines the presence or absence of an object to be recognized in the image data acquired from the imaging devices 1 and 2. When the image processing device determines that the object to be recognized is present, it sends out information indicating that the object is present, and an output device, when receiving the information indicating that the object to be recognized is present, informs the outside that the object to be recognized is present.