A projection type display device includes a lamp, polarization means (21) for converting light emitted from the lamp to polarized light, a liquid crystal panel for modulating the polarized light to form an image light, a projection lens (7) for projecting the image light, fans (11R, 12G, 23B) for taking outside air in and for supplying the outside air to the polarization means and the liquid crystal panel, a filter for collecting dust contained in the outside air, a first detection means for detecting temperature T1 of the outside air, a first control means for controlling the number of revolutions of the fan in response to temperature T1, a second detection means for detecting temperature T2 of the polarization means, a storage means for storing reference temperature T3, and a second control means. The second control means issues a warning or stops the projection type display device when temperature T2 is higher than reference temperature T3.