The present disclosure provides a more easy-to-use projection system including an imaging unit that captures an image of a specific area, which is specified by light excited by light having a predetermined wavelength, in a subject, a projector that projects an image of the specific area by visible light, a controller that controls such that the image of the specific area and associated information associated with the image of the specific area are projected onto the subject, and an optical unit that causes an optical path of the imaging unit with respect to the subject and an optical path of the projector with respect to the subject to coincide with each other.