A pulse generator with large amplitude of 160 V and fast rise time of less than 0.4 ns has been built using a coaxial cable as a capacitor. By combining with the anomalous Hall effect technique for a single magnetic nanodot, magnetization response of one Co/Pt nanodot of 400 nm in diameter to the pulse was examined. By applying a pulse field with the maximum amplitude of 740 Oe and the duration of 10 ns, magnetization switching of the dot by the pulse was successfully observed. The pulse amplitude dependence of switching field suggested that the pulse field and the dc bias field could be treated as a simple summation of the both fields in the time scale of 10 ns. All the results of magnetization switching by the pulse field could be explained qualitatively by classical thermal relaxation process.