An electrometer includes a sensing module and a control module. The sensing module includes an electrostatic sensing element. The electrostatic sensing element includes two opposite ends. Each end of the electrostatic sensing element is electrically connected to the control module. When an object with electrostatic charge is near but does not touch the electrostatic sensing element, the resistance of the electrostatic sensing element can be changed. The control module electrically connect to the electrostatic sensing element, the control module measures the resistance variation ΔR of the electrostatic sensing element and converts the resistance variation ΔR into the static electricity potential.