A method of detecting a foreign object on a stage according to one aspect of the present disclosure includes acquiring first position information of a first pattern included in a first image in a reference state of a surface of the stage capable of attracting an object to be inspected; acquiring second position information of a second pattern included in a second image of the surface, the second image being obtained after obtaining the first image; and detecting one or more foreign objects on the surface by comparing the first position information and the second position information.