A circuit measuring device and a method thereof are provided. A voltage source supplies a common voltage such that a calibration current having a preset current value flows from a current-voltage converter to a final test machine. The current-voltage converter converts the calibration current into a calibration voltage. At this time, a voltage sensing component senses a voltage between an input terminal and an output terminal of the current-voltage converter to output sensed calibration data. The current-voltage converter converts a tested current outputted by a tested circuit into a tested voltage. At this time, the voltage sensing component senses the voltage between the input terminal and the output terminal of the current-voltage converter to output actual sensed data. When the final test machine determines that a difference between the sensed calibration data and the actual sensed data is larger than a threshold, the tested circuit is adjusted.