A peripheral device includes a manual operable device, a baseplate for carrying the manual operable device and a circuit board. The baseplate includes a plate edge extending substantially along an x-axis; a left plate indent edge, a left convex edge, a substantially linear edge, a right convex edge and a right plate indent edge are sequentially disposed on the plate edge. The circuit board includes a main portion and a flexible extension. The main portion generates a control signal in response to a triggering event at the manual operable device. The flexible extension extends substantially along a y-axis, and includes an upper end, a lower end, a y-axial left edge and a y-axial right edge; the upper end is connected to the main portion, the lower end is connected to an external connection point, and the control signal is transmitted to the external connection point via the flexible extension.