An image display medium which implements multi-color display with a small number of kinds of particles and avoids a reduction in resolution of images, and an image writing device. The image display medium has a structure with a transparent display substrate, a colored back substrate, a spacer for constantly maintaining inter-substrate space, and white particles and black particles. The image display device is provided with the image display medium, an electrode head and a voltage application section. The electrode head implements monochrome display by moving the white particles and the black particles one to the display substrate side and the other to the back substrate side, by applying dc voltages between the substrates. When multi-color display is to be implemented, the electrode head applies ac voltages between the substrates and moves the particles to peripheries of portions so as to expose the back substrate at those portions.