A method for measuring a surface potential of a portion of material, wherein an electrically conductive detection tip is placed above a surface of said portion of material, with a first piezoelectric actuator arranged to control a mean distance of the detection tip above said surface of the portion of material, and a second piezoelectric actuator arranged to control a mechanical oscillation of said detection tip above said surface of the portion of material as a function of a voltage existing between two control electrodes (2a, 2b) of said second piezoelectric actuator, said method comprising the following steps: - applying a measurement voltage (V M) between the detection tip and the portion of material, said measurement voltage comprising a DC component (V M) and an AC component (V M (ω E)) having a selected angular frequency of excitation (ω E); - simultaneously detecting variations in the instant height (h) of the detection tip; - measuring an amplitude of a component (h(ω E)) of said variations in the instant height of the detection tip, for said angular frequency of excitation; and - adjusting a value of the DC component (V M) of the measurement voltage so as to reduce or cancel the amplitude of the component (h(ω E)) of the variations in the instant height of the detection tip for the angular frequency of excitation, the adjusted value of said DC component of the measurement voltage constituting a result of the measurement of the surface potential of the portion of material; the method being characterized in that, while the variations in the instant height (h) of the detection tip are being detected: - the two driving electrodes (2a, 2b) of the second piezoelectric actuator are electrically connected to two respective reference terminals (21a, 21b); and - a control voltage is applied between the two driving electrodes (2a, 2b) of the second piezoelectric actuator through the two reference terminals (21a, 21b), said control voltage having a zero AC component amplitude for the angular frequency of excitation (ω E). - applying a measurement voltage (V M) between the detection tip and the portion of material, said measurement voltage comprising a DC component (V M) and an AC component (V M (ω E)) having a selected angular frequency of excitation (ω E); - simultaneously detecting variations in the instant height (h) of the detection tip; - measuring an amplitude of a component (h(ω E)) of said variations in the instant height of the detection tip, for said angular frequency of excitation; and - adjusting a value of the DC component (V M) of the measurement voltage so as to reduce or cancel the amplitude of the component (h(ω E)) of the variations in the instant height of the detection tip for the angular frequency of excitation, the adjusted value of said DC component of the measurement voltage constituting a result of the measurement of the surface potential of the portion of material; - the two driving electrodes (2a, 2b) of the second piezoelectric actuator are electrically connected to two respective reference terminals (21a, 21b); and - a control voltage is applied between the two driving electrodes (2a, 2b) of the second piezoelectric actuator through the two reference terminals (21a, 21b), said control voltage having a zero AC component amplitude for the angular frequency of excitation (ω E).