A keyboard includes a base plate, a plurality of keys and a backlight module. The base plate has a short axis direction and a long axis direction. The keys are disposed on the base plate along the long axis direction, and the keys are arranged to form a plurality of rows. The backlight module is disposed on the base plate and includes a shielding sheet, a light guide plate and a reflecting sheet. The light guide plate is disposed on a lower surface of the shielding sheet. The light guide plate includes a plurality of long openings, and each of the long openings has at least one long side. The long side is parallel to the long axis direction, and each of the long openings has a central axis. The central axis is located between two adjacent rows on which the keys are disposed.