Nanometer-scale pit formation by the application of pulse voltage was performed on highly oriented graphite in air with the simultaneous measurement of tip current. The tip current was measured to be on the order of microamperes. Regardless of the high current, the pit was not formed at pulse voltages less than a critical value. It is confirmed by the quantitative measurement of the current that high current is less important for pit formation under experimental conditions. The measurement of the critical voltage as a function of the tunnel resistance suggested the significance of high electric field for pit formation.