An illuminated keyboard including a backlight module and a key structure is provided. The backlight module includes a reflector, a light guide plate, a light source, and a light shielding plate. The light guide plate is disposed on the reflector, and a surface of the light guide plate facing the reflector has multiple microstructures. The light source is located on a light incident surface side of the light guide plate. The light shielding plate is disposed on the light guide plate. The light shielding plate has a shielding area and a light transmissive area, and the microstructures are correspondingly disposed in the light transmissive area. The key structure has multiple keycaps. In the microstructures correspondingly disposed under one single keycap, peaks of any two microstructures adjacent to each other keep different distances from the surface of the light guide plate facing the reflector.