A writing device for writing an image to a display medium, the writing device applies a voltage between a pair of electroconductive layers and irradiates light onto a photosensitive layer. The light irradiates onto a region of the photosensitive layer that overlaps a region of the display layer where liquid crystal of a first display layer undergoes transition to the light-reflecting state, and applies a voltage between the pair of electroconductive layers for a time period such that a voltage equal to or larger than a second threshold voltage is applied to a region of the display layer unit where the liquid crystal of the first display layer is to undergo transition to the light-reflecting state, and a voltage smaller than the second threshold voltage is applied to a region of the display layer unit overlapped by a region of the photosensitive layer to which no light is irradiated.