PURPOSE: To provide a digital voltage measuring device for measuring an output voltage of wide range of elements to be measured, in the maximum effective orders of magnitude that can be read, which is constantly retained in a digital voltmeter.

CONSTITUTION: A divided voltage circuit 12 is placed and connected to between an element D to be measured and the input step of a digital voltmeter 10. A control part 11 is provided, which processes the signal of an output digital data of an A/D converter 3 of the digital voltmeter. When it is judged by the control part that a digital data is not in the maximum effective orders of magnitude that can be read of the A/D converter, voltage division ratios of the divided voltage circuit 12 and of a range switching circuit 2 are switched so that the digital data is expressed in the effective orders of magnitude, and the output voltage of the element to be measured is proportionally reduced once. The digital data thus provided is multiplied by an inverse number of the division voltage ratio of the divided voltage circuit 12, and is thus converted into a digital data corresponding to the output voltage, and is displayed by a digital display part 4. The voltage of wide range can thus be constantly measured and displayed in the maximum effective orders of magnitude that can be read.