A DC power supply system includes: nodes to connect to a DC bus and constitute a DC grid with the bus; a power management apparatus that manages the power demand of the entire grid; and a starter device that makes the nodes start up and connect to the bus one by one in an order in a state where the bus is down to start up the entire grid. The starter device supplies start-up power through a power supply line to start up each node. The starter device diagnoses nodes to be diagnosed selected from among the nodes before supply of the power to determine the abnormality from a response with respect to a diagnostic signal supplied to the nodes through the start-up power supply line. When the node diagnosed is determined to be normal, the starter device supplies the start-up power thereto and connects it to the bus.