A power supply system includes a plurality of sweep modules. Each sweep module includes a battery module, an input and output circuit, a switching element, a capacitor, and a line. The input and output circuit connects the battery module to a main line. The switching element switches between connection and disconnection between the battery module and the main line. The capacitor is attached in parallel to the battery module. The line connects the input and output circuit to the battery module. The line is maintained in a state in which a loop portion is formed.