An in-vehicle power supply system comprising: a main power supply (BAT 1) configured to supply power; one or more power supply hubs; a plurality of electronic devices; a main power cable configured to connect the one or more power supply hubs to the main power supply (BAT 1); a sub power cable configured to connect each of the plurality of electronic devices to any one of the one or more power supply hubs; and a control unit configured to turn on/off power supply to each of the plurality of electronic devices through a power supply hub connected to the electronic device, wherein current flowing through each of the plurality of electronic devices is classified into continuous current, intermittent current, or inrush current, the plurality of electronic devices are each classified into either one of a continuous load through which continuous current flows and an intermittent load through which intermittent current flows, and a voltage after a voltage drop caused by the continuous current flowing through the continuous load is designed to be higher than a rated voltage specified for at least one of the plurality of electronic devices, a voltage after a voltage drop caused by the continuous current and the intermittent current flowing respectively through the continuous load and the intermittent load is designed to be higher than a minimum performance guarantee voltage which is a minimum voltage which guarantees operation of the plurality of electric devices with certain performance specified for each of the plurality of electronic devices, and a voltage after a voltage drop caused by the continuous current and the inrush current flowing respectively through the continuous load and the intermittent load is designed to be higher than a minimum function maintaining voltage which does not satisfy a certain performance specified for each of the plurality of electric devices but allows operation of at least a basic function of the plurality of electric devices. a main power supply (BAT 1) configured to supply power; one or more power supply hubs; a plurality of electronic devices; a main power cable configured to connect the one or more power supply hubs to the main power supply (BAT 1); a sub power cable configured to connect each of the plurality of electronic devices to any one of the one or more power supply hubs; and a control unit configured to turn on/off power supply to each of the plurality of electronic devices through a power supply hub connected to the electronic device, wherein current flowing through each of the plurality of electronic devices is classified into continuous current, intermittent current, or inrush current, the plurality of electronic devices are each classified into either one of a continuous load through which continuous current flows and an intermittent load through which intermittent current flows, and a voltage after a voltage drop caused by the continuous current flowing through the continuous load is designed to be higher than a rated voltage specified for at least one of the plurality of electronic devices, a voltage after a voltage drop caused by the continuous current and the intermittent current flowing respectively through the continuous load and the intermittent load is designed to be higher than a minimum performance guarantee voltage which is a minimum voltage which guarantees operation of the plurality of electric devices with certain performance specified for each of the plurality of electronic devices, and a voltage after a voltage drop caused by the continuous current and the inrush current flowing respectively through the continuous load and the intermittent load is designed to be higher than a minimum function maintaining voltage which does not satisfy a certain performance specified for each of the plurality of electric devices but allows operation of at least a basic function of the plurality of electric devices.