The present invention provides an input device such as a mouse which has a unique construction with integrated key plates and integrated side grips. In one embodiment, the input device comprises a housing, which includes a bottom case and an upper member disposed above the bottom case. The upper member includes a palm rest configured to support a user's palm and at least one key plate extending continuously from the palm rest to form a hinge between the at least one key plate and the palm rest without a gap. The key plate is movable in bending relative to the palm rest at the hinge to activate a key switch. The left side grip and the right side grip are formed on a single piece top case connected between the upper member and the bottom case. The left side grip and right side grip typically have concave surfaces.