To provide a DC pantograph arc measuring method that allows an arc generated by a bouncing pantograph to be measured, until the pantograph current becomes zero.

In an electric rolling stock whose pantographs 2 are connected with a high-voltage bus bar 3 in a DC current zone, a clamp ammeter for measuring current and a personal computer 5 which computes and records the measured current are used to calculate the arc extinction time for the closed circuit comprising a trolley line 1, pantographs, and the high-voltage bus bar, thereby measuring the arc 6 generated by a bouncing pantograph, until the pantograph current becomes zero.