A displaying device adapted to a screen is provided. The displaying device includes a transparent pyramid, a movable support, and an image conversion unit. The movable support is connected to the transparent pyramid to move the transparent pyramid between a first location and a second location which is different from the first location. The first location is the position on the screen. The image conversion unit is configured to receive image data. When the transparent pyramid moves to the first location, the image conversion unit converts the image data to a holographic image displayed on the screen, and the transparent pyramid generates a 3D hologram based on the holographic image.