A keyboard device includes a base plate, a butterfly-type connecting element and a keycap assembly. The keycap assembly includes a coupling frame and a keycap. The coupling frame includes a first coupling part. The keycap includes a second coupling part. The butterfly-type connecting element is connected with the base plate and the coupling frame. The coupling frame and the butterfly-type connecting element are combined together through the first coupling part and the second coupling part. When the pressing force is acted on a corner of the keycap, the pressing force can be transferred to the whole keycap through the coupling frame. Consequently, the pressing force can be effectively transferred.