The present invention relates to a rear projection type image display device comprising projection lenses (2, 3) for projecting an image displayed on an image display element onto a transmission type screen (6) on a larger scale, an optical path turn-back mirror (7) for turning back halfway a light beam projected from the projection lenses, and a drive circuit for displaying an image on the image display element, that are fixedly housed within a housing (5). When a diagonal size of the transmission type screen (6), the depth of the housing (5), and the length from a lower end of the screen (6) to a lower end of the housing (5), are assumed to be SS (inch), D (inch), and L (inch), respectively, the following conditions are satisfied: SS>40, D≦SS/3.0, L≦SS/10.9