The present invention discloses a potential difference meter for the measurement of direct current voltage, which is provided with four step disks and one double wire sliding disk. The five disks respectively consist of a measuring disk and a replacing disk which has the same resistance value. The working current is divided into two branches with the proportion of 10 to 1 between two electric brushes of the first step disk. Two disks of each branch are connected in parallel with the current ratio of 10 to 1. Besides the first step disk, the electric brush of the measuring disk of each step disk and the electric brush of the replacing disk of each stepper disk are connected through a resistor or conducting wires. Each step disk or double wire sliding disk has no auxiliary disk, thus the volume of the device is reduced, and the manufacturing cost of the device is reduced; meanwhile, the five measuring disks are connected through conducting wires, and the influence of the variation and the thermoelectric potential is eliminated.