The objective of the present invention is to provide an object detection method such that an object such as a vehicle can be detected from an image captured by an on-board camera even when a lens of the on-board camera is dirty. In order to achieve the objective, in this object detection method for detecting an object included in a captured image, an original image including the object to be detected is prepared from the captured image, a processed image is generated from the prepared original image by applying predetermined processing to the original image, and learning regarding restoration of an image of the object to be detected is performed using the original image and the processed image.