An electrostatic-controlled torsion pendulum combined with a scanning conducting probe is used to measure the temporal and spatial variations of the surface potential on test mass. The apparatus can work in static and scanning modes. Temporal variation of the surface potential can be measured with the static mode, and its voltage variation with a level of $15\text{ }\text{ }\ensuremath{\mu}\mathrm{V}/{\mathrm{Hz}}^{1/2}$ at 0.03 Hz has been achieved for a $5\ifmmode\times\else\texttimes\fi{}5\text{ }\text{ }{\mathrm{mm}}^{2}$ area. The spatial distribution of the surface potential can be measured with the scanning mode, and the surface potential distribution can be obtained at a level of $330\text{ }\text{ }\ensuremath{\mu}\mathrm{V}$ at 0.125 mm spatial resolution. The experimental results tell us that the apparatus provide a new way to investigate the charge distribution and its variation, which is very useful in helping to understand the physical mechanism of the surface charge distribution of an actual object.