Light source device and projector

A light source device comprising:

• a light emitting tube having a light emitting section having a pair of electrodes disposed inside the light emitting section;
• a reflecting mirror adapted to reflect a luminous flux emitted from the light emitting section;
• and
• a tubular member disposed on a forward side of light emission of the reflecting mirror, and surrounding the light emitting tube,
• wherein the tubular member has a pair of air circulating units communicating inside and outside of the tubular member and adapted to allow introduction of external air from the forward side toward a backward side of the light emission in a vertically symmetrical manner on a center axis of the light emitting tube,
• inside the air circulating unit there is disposed an air flow guide member adapted to straighten the air introduced in the tubular member and make the air flow to the light emitting tube, and
• the air flow guide member is pivoted rotatably around a predetermined rotational axis with respect to the air circulating unit under own weight of the air flow guide member, and rotates to thereby open and block at least a part of a flow passage inside the air circulating unit.