A power supply system of a fuel cell of a vehicle for supplying electric power to an external load, the power supply system using user authentication and comprising: a tagging device configured to receive user information of a user terminal; an identity authentication unit configured to compare the user information inputted through the tagging device with previously stored authentication information, and output a use authority signal when the user information matches the authentication information; a power module configured to produce electric power by a chemical reaction between hydrogen and oxygen; a battery configured to receive and be charged with electric power produced by the power module; an output terminal connected to the battery to output electric power stored in the battery; and an integrated control unit configured to control electric power to be outputted through the output terminal when the identity authentication unit outputs the use authority signal, characterized in that the battery includes: a high-voltage battery configured to store a first voltage supplied through a bidirectional high voltage DC/DC converter, which receives electric power produced by the power module and converts a voltage received from the power module into a first voltage; and a low-voltage battery configured to store a second voltage, the second voltage having a voltage lower than that of the first voltage, supplied through a low voltage DC-DC converter, which receives electric power produced by the power module and converts the voltage received from the power module into a second voltage to be lower than the first voltage, wherein the output terminal is disposed adjacent the tagging device, and wherein the output terminal includes: a high-voltage output terminal connected to the high-voltage battery to output power at the first voltage; and a low-voltage output terminal connected to the low-voltage battery to output power at the second voltage. a tagging device configured to receive user information of a user terminal; an identity authentication unit configured to compare the user information inputted through the tagging device with previously stored authentication information, and output a use authority signal when the user information matches the authentication information; a power module configured to produce electric power by a chemical reaction between hydrogen and oxygen; a battery configured to receive and be charged with electric power produced by the power module; an output terminal connected to the battery to output electric power stored in the battery; and an integrated control unit configured to control electric power to be outputted through the output terminal when the identity authentication unit outputs the use authority signal, characterized in that the battery includes: a high-voltage battery configured to store a first voltage supplied through a bidirectional high voltage DC/DC converter, which receives electric power produced by the power module and converts a voltage received from the power module into a first voltage; and a low-voltage battery configured to store a second voltage, the second voltage having a voltage lower than that of the first voltage, supplied through a low voltage DC-DC converter, which receives electric power produced by the power module and converts the voltage received from the power module into a second voltage to be lower than the first voltage, wherein the output terminal is disposed adjacent the tagging device, and wherein the output terminal includes: a high-voltage output terminal connected to the high-voltage battery to output power at the first voltage; and a low-voltage output terminal connected to the low-voltage battery to output power at the second voltage. a high-voltage battery configured to store a first voltage supplied through a bidirectional high voltage DC/DC converter, which receives electric power produced by the power module and converts a voltage received from the power module into a first voltage; and a low-voltage battery configured to store a second voltage, the second voltage having a voltage lower than that of the first voltage, supplied through a low voltage DC-DC converter, which receives electric power produced by the power module and converts the voltage received from the power module into a second voltage to be lower than the first voltage, wherein the output terminal is disposed adjacent the tagging device, and wherein the output terminal includes: a high-voltage output terminal connected to the high-voltage battery to output power at the first voltage; and a low-voltage output terminal connected to the low-voltage battery to output power at the second voltage. a high-voltage output terminal connected to the high-voltage battery to output power at the first voltage; and a low-voltage output terminal connected to the low-voltage battery to output power at the second voltage.