High voltage power apparatus can be damaged by lightning which is an impulse voltage seen in nature. It is, therefore, very important to investigate the behavior of the equipments under the impulse voltage, to develop reliable insulation designs. When the impulse voltages measured which is generated in the laboratory, it has been revealed that the signal is noisy. These noises introduce difficulties determining characteristic parameters identifying impulse voltage. For that reason, it is important to de-noise the impulse voltage signal. In this study, wavelet transform is used to filter out the noise. It is seen that wavelet transform gives efficient and successful results for de-noising of the impulse voltage waveform.