A light source device (40) attached to an optical equipment provided with
a light-source cooling fan (3) has a light source (401), a reflector
(402), a light-transmissive component (51) that closes the
light-irradiation side of the reflector (402) and a light source housing
(50) that houses the above components. An opening (402A) for introducing
a cooling air is formed on the reflector (402) and an opening (52) is
formed on the light source housing (50) at a position corresponding to
the light source housing (50). A duct (53) of which light-irradiation
side is opened is provided on the opening (52). When the light source
device (40) is attached to the optical equipment, the duct (53) protrudes
toward the light-irradiation side to be connected with the fan (3). The
opening (52) is opened in accordance therewith, so that the air from the
fan (3) is introduced into the reflector (402).