In a projection-type image display device, a driven member of a screen is displaced in a plane parallel to the screen. The driven member can be a Fresnel lens or a diffusing member. An elastic retaining unit holds the driven member in such a manner as to be capable of moving in the plane parallel to the screen, and a pair of driving sources applies driving forces in mutually intersecting directions to the driven member. A control circuit drives the pair of driving sources with driving waveforms having a prescribed phase difference therebetween so that the driven member makes continuous motion in a plane parallel to the screen when an image is projected.