A power source supervisory apparatus is provided with a connection path that connects between a first path and a second path, an inter-path switch SW provided on the connection path, a current limiting element disposed to be in series to the inter-path switch SW on the connection path enabling a conduction from a first path side to a second path side under a current limiting state and obstructing conduction from the second path side to the first path side, a supervisory unit that supervises occurrence of a voltage drop on the first path in a state where the inter-switch is closed, and a switch operation unit that opens the inter-path switch SW when the supervisory unit determines that a voltage drop occurs on the first path.