A key device includes a substrate, a key cap and a restoring member. The substrate includes a top surface and two pivot seats protruding on the top surface. The pivot seats are spaced from each other. Each pivot seat has an eave portion laterally extending from a top thereof. The eave portion has a bottom edge. The key cap is above the top surface. The key cap includes a side edge and two extending arms extending from the side edge. An end of each extending arm has a pivoting portion. The pivoting portions pivotally abut against the bottom edges of the eave portions respectively without contacting the top surface of the substrate. The restoring member is between the substrate and the key cap and abuts against a bottom of the key cap.