To provide a projection-type image display device capable of both minimizing the lowering of a cooling capability and simplifying the maintenance of a filter.

The projection-type image display device includes: a filter material 2 for filtering outside air taken into a casing; a loop-shaped filter frame 1 to which the filter material 2 can be mounted; a drive mechanism 4 for rotating and moving the filter frame in a loop direction of the loop shape; and a dust removal brush 5 brought into contact with the filter material 2 while being spun at a predetermined position. The filter material 2 is mounted to a part of a loop-shaped surface of the filter frame 1. The filter material is not mounted but a ventilation part 3 is provided in the other part of the loop-shaped surface of the filter frame 1.