The error of instrument transformers is measured by connecting the external burden with the secondary terminal of the instrument transformers. Because the error of transformer is affected by the apparent power and power factor of the external burden, an accurate measurement of burden is important for transformer evaluation. We have developed the burden evaluation equipment for both potential transformer and current transformer by employing the series resistor in the range of $20m{Omega}{sim}5{Omega}$ and the parallel resistor in the range of $1M{Omega}{sim}500{Omega}$, respectively, together with visual basic program. We could reduce testing time more than 5 times by employing method developed in this study, compared with that developed in past. This method shows more better reliability by analyzing the evaluation results and fitting graphs of burden measurements. The test results of the developed system is compared with those obtained in the power meter analyzer to verify the validity.