A keyboard includes a backlight module, a base plate, a membrane circuit disposed on the base plate, and a plurality of key structures disposed on the membrane circuit. The backlight module includes a light source, a reflective layer, a light guide layer, and a shielding layer. The light source is disposed corresponding to the light guide layer. The light guide layer is located between the shielding layer and the reflective layer. The light guide layer has a through-hole. The shielding layer and the reflective layer are in contact with each other in the through-hole of the light guide layer. The base plate is disposed on the shielding layer. The base plate has a positioning portion disposed corresponding to the through-hole of the light guide layer, which protrudes toward the reflective layer or the membrane circuit.