An illumination device includes a light source device including an ellipsoidal reflector with a reflecting concave surface and a light emitting tube having an emission center in the vicinity of a first focal position of the ellipsoidal reflector, and defining a first focal position and a second focal position of the ellipsoidal reflector in a cross-sectional plane in a first virtual plane including a center axis of the ellipsoidal reflector as F1 and F2, respectively, and defining a first focal position and a second focal position of the ellipsoidal reflector in a cross-sectional plane in a second virtual plane including a center axis of the ellipsoidal reflector and perpendicular to the first virtual plane as F1′ and F2′, respectively, the ellipsoidal reflector has a rotationally asymmetrical concave shape having F1 and F1′ at the same position, and F2 located between the F2′ and the ellipsoidal reflector.