A keyboard includes a membrane circuit board, a luminous key, a light-emitting element and a plastic film layer. The luminous key has a keycap with a light-transmissible part. The luminous key is configured for triggering a membrane switch of the membrane circuit board. The light-emitting element is disposed on the membrane circuit board and arranged under the light-transmissible part for emitting a light beam. The plastic film layer is disposed on the membrane circuit board, and includes a convex structure, which is integrally formed with the plastic film layer. The light-emitting element is enclosed by the convex structure. The convex structure has an opening aligned with the light-emitting element. The keyboard of the present invention has enhanced production yield and reduced light leakage.