The invention first relates to a surge voltage measuring device, connected to an input voltage to the voltage transforming unit attenuating a predetermined ratio, the multi-stage to the voltage transforming part rear end for amplifying the voltage at a predetermined amplification ratio is set for each one, and a second buffer section, is the installation in the first buffer parts of the rear end of the first analog / digital conversion section for converting the first buffer parts of the output voltage to a digital signal, is the installation in the second buffer portion downstream of the second buffer portion and second analog / digital converting unit, and first and second memory section to the signal output from the first and second analog / digital converting unit stores each of the first and second memory portion for converting the output voltage into a digital signal is installed on the rear end, the second memory unit a signal is up-bit (bit) or more, or if the set is less than the minimum bit selected by the second memory portion Works the signal voltage is set, otherwise selecting the first memory portion signal to the normal voltage which consists of a control voltage measurement. According to the configuration of the present invention described above, the present invention can be measured in real-time the normal voltage and the surge voltage of the measuring line, it is possible to prevent a failure of the equipment caused by the surge voltage in advance. Surge voltage, a buffer, a transformer, an analog / digital converter (ADC), a multiplexer (MUX)