A key device includes a substrate having an assembling area, a keycap, and a restoring member. A pivot coupling member and an elastic arm are provided in the assembling area. The pivot coupling member has a pivot axis, and the elastic arm is extending in a direction parallel to the pivot axis. The elastic arm includes a limiting member protruding out of the substrate. The keycap is disposed above the assembling area. A connection arm is extending from the keycap and includes a pivot portion pivoted with the pivot coupling member, so that the keycap is swingable relative to the substrate. The keycap further includes a limiting groove for detachably fitted with the limiting member. The restoring member is disposed between the substrate and the keycap. The restoring member is adapted to provide a restoring force for swinging the keycap relative to the substrate.