A key structure includes a base plate, an illumination module, a switch circuit board, a metallic elastic element, a supporting element, a metallic pressing plate and a covering member. The metallic elastic element is disposed on the switch circuit board. The supporting element is located beside the metallic elastic element. An edge of the metallic pressing plate is fixed on the supporting element. As the metallic pressing plate is swung relative to the base plate to push the metallic elastic element, the switch circuit board is triggered by the metallic elastic element. The covering member covers the base plate and the metallic pressing plate. The covering member has a light-transmissible region. A light beam from the illumination module passes through the light-transmissible region. Consequently, the key structure is illuminated.