A projection device includes an invisible image sensor, a projector, a visible image sensor, an imaging optical system, a light guide, and a light shield. The invisible image sensor captures an invisible light image of a subject. The projector projects a projection image based on the invisible light image onto the subject with visible light. The visible image sensor captures an image of the subject onto which the projection image is projected. The system includes a diaphragm. The light guide guides light to enter the system and light exited from the projector. The light shield is disposed at a space from the light guide. A diaphragm value is set so that a length difference between an optical length from a near point in a DOF of the system and an optical length from the light shield is longer than a front DOF from the subject.