Keyboard device

A keyboard device, comprising:

• plural key structures exposed outside the keyboard device;
• a switch circuit board located under the plural key structures, wherein when the switch circuit board is triggered by one of the plural key structures, a corresponding key signal is generated, wherein the switch circuit board comprises a hollow region;
• an elastic cover disposed on the switch circuit board, wherein the hollow region is covered by the elastic cover, so that a foreign liquid is prevented from entering the switch circuit board;
• and
• a seal element disposed on sidewalls of the switch circuit board, so that a sealed region is formed between the switch circuit board and the elastic cover to prevent the foreign liquid from entering the switch circuit board, wherein when a volume of an inner gas within the sealed region increases, the elastic cover is subjected to expansion in response to elasticity of the elastic cover and the volume of the inner gas, wherein when the volume of the inner gas within the sealed region decreases, the elastic cover is subjected to contraction in response to elasticity of the elastic cover and the volume of the inner gas.