An electrometer includes a sensing module and a control module. The sensing module includes a plurality of electrostatic sensing elements and a plurality of second electrodes. The plurality of electrostatic sensing elements are single walled carbon nanotubes or few-walled carbon nanotubes. The plurality of electrostatic sensing elements and the plurality of second electrodes are alternately arranged in a series connection. The control module is coupled to the two ends of the series connection and configured to measure a resistance variation ΔR of the series connection and convert the resistance variation ΔR into a static electricity potential.