To provide a projection type image display device which can remove dust sticking to light valves.

Each fun device 21 is disposed so that an air current created by rotation of a fun is blown upwards through an opening 21a. The liquid crystal light valves 31, 32, and 33 are disposed above the respective openings 21a such that polarizer plates on the incoming side, panels, and polarizer plates on the outgoing side are separated from one another. Thereby, air current is blown onto the exposed faces of the polarizer plates and the exposed faces of the panels. The rotating speed of the motor which drives the fans are controlled by a motor driver (drive IC) such that first rotating speed (rotation in a cooling period) and second rotating speed (rotation higher than the rotation in the cooling period) are available. Dust sticking to the liquid crystal light valves are blown off with the second rotating speed.