A projection display device that includes: a light source unit 1 that includes a discharge lamp 2 as a light source; an image formation unit; a projection optical system; and a light source cooling unit that cools the light source unit. The light source unit is disposed so that a lamp axis that connects two discharge electrodes of the discharge lamp is orthogonal to a projecting direction of the projection optical system, and the light source unit includes: a concave mirror 3; and a transparent part 4 that covers an opening of the concave mirror. The light source cooling unit includes: a blowing fan that supplies cooling air; a plurality of air blowing ports 6a and 6b disposed at the concave mirror or a connecting part that connects the concave mirror and the transparent part; an air duct 9 that connects the air blowing ports and the blowing fan; a branch switching valve 10a that is disposed in the air duct and switches between a plurality of branch flow paths so as to allow the cooling air to flow therethrough; and a control valve that is provided for each of the air blowing ports and rotated around a supporting axis by the action of gravity depending on a posture of the light source cooling unit, thereby controlling a wind direction so that the cooling air is blown from above the discharge lamp. The top of the light source lamp is cooled effectively regardless of the installation posture of the projection display device.