An illuminating device according to the present invention comprises a first reflector for irradiating forward light beams from a light source, a second reflector that has an aperture and is disposed in front of the first reflector so as to reflect toward the light source the light beams from the first reflector to condense the light beams, a third reflector disposed so as to make the light beams condensed by the second reflector exit through the aperture, and a reflector moving means that moves the second reflector or the third reflector along an optical axis.