An illuminated keyboard with an optical switch is provided. The illuminated keyboard includes a circuit board and plural keys. The circuit board includes plural light-emitting elements. Each light-emitting element is aligned with the corresponding key. The key includes a keycap, a housing, a triggering post, a light guide element and a light guide frame. The keycap is located over the housing. The triggering post, the light guide element and the light guide frame are disposed within the housing. Moreover, the light guide frame is arranged around the triggering post. After a light beam emitted by the light-emitting element is introduced into the housing, the light beam is guided to the light guide frame by the light guide element, and the light beam is scattered to a region around the triggering post and outputted from the keycap.