A method and a device for locating internal arcing that occurs in a compartment (CPi) of a gas-insulated line (L), each compartment being provided with at least one pressure sensor (Pi). The method comprises: triggering pressure measurements in a compartment as soon as the difference between the currents that flow through two current toroids (TCi) around two adjacent compartments exceeds a threshold value indicating the occurrence of internal arcing in the compartment; calculating a period Δt that separates the time at which the pressure detector began to detect a pressure variation and the time at which the internal arcing occurred; and calculating a distance d that separates the place at which the internal arc is formed from the position of the pressure sensor using the equation d=V/Δt in which V is the speed of sound in the gas.