To address the problem that electric leak detecting devices using ring-shaped magnetic elements have their own limit in downsizing and, where thick electric wires are used, the ring-shaped magnetic elements themselves become larger, entailing the further problem that arranging ring-shaped magnetic elements for already installed wires is no easy work.

An electric leak detecting device to be installed on a pair of power supply lines connecting a power source and loads comprises a pair of holding means each holding one or the other of the pair of power supply lines; fixing means that fixes the pair of holding means to each other at prescribed spacing in-between; a pair of magnetic elements each arranged on one or the other of the pair of holding means in parallel to the power supply lines; detecting means that detects any difference in magnetic resistance effect between the pair of magnetic elements; and drive means that supplies drive currents to the magnetic elements.