A power supply system comprising: a converter unit configured to perform constant voltage control of outputting a predetermined constant voltage when an output current value falls within a range of equal to or lower than a predetermined value, and to output a voltage to a load; a secondary battery; a voltage control unit connected between the load and the secondary battery and configured to change a discharge voltage of the secondary battery to an output voltage target value that is a target value for a voltage to be outputted to the load, and output the discharge voltage to the load; and an output current value acquisition unit configured to acquire an output current value of the converter unit, wherein the voltage control unit is configured to - set the output voltage target value such that, when the output current value acquired by the output current value acquisition unit is equal to or higher than a first threshold lower than the predetermined value, the output voltage target value increases with increase of the output current value until the output voltage target value exceeds a value of the predetermined constant voltage of the converter unit, and - set the output voltage target value to exceed the value of the predetermined constant voltage of the converter unit when the output current value is between the first threshold and a second threshold, which is greater than the first threshold, and when said output current value is exceeding a point, at which the output voltage target value coincides with the predetermined constant voltage of the converter unit, and lower than the predetermined value; and wherein the converter unit includes a plurality of convertors (102a, 102b, 102c, 102d) connected in parallel and having a current share function based on a current share signal, and the output current value acquisition unit acquires the output current value of the converter unit by receiving the current share signal from the converter unit. a converter unit configured to perform constant voltage control of outputting a predetermined constant voltage when an output current value falls within a range of equal to or lower than a predetermined value, and to output a voltage to a load; a secondary battery; a voltage control unit connected between the load and the secondary battery and configured to change a discharge voltage of the secondary battery to an output voltage target value that is a target value for a voltage to be outputted to the load, and output the discharge voltage to the load; and an output current value acquisition unit configured to acquire an output current value of the converter unit, wherein the voltage control unit is configured to - set the output voltage target value such that, when the output current value acquired by the output current value acquisition unit is equal to or higher than a first threshold lower than the predetermined value, the output voltage target value increases with increase of the output current value until the output voltage target value exceeds a value of the predetermined constant voltage of the converter unit, and - set the output voltage target value to exceed the value of the predetermined constant voltage of the converter unit when the output current value is between the first threshold and a second threshold, which is greater than the first threshold, and when said output current value is exceeding a point, at which the output voltage target value coincides with the predetermined constant voltage of the converter unit, and lower than the predetermined value; and wherein - set the output voltage target value such that, when the output current value acquired by the output current value acquisition unit is equal to or higher than a first threshold lower than the predetermined value, the output voltage target value increases with increase of the output current value until the output voltage target value exceeds a value of the predetermined constant voltage of the converter unit, and - set the output voltage target value to exceed the value of the predetermined constant voltage of the converter unit when the output current value is between the first threshold and a second threshold, which is greater than the first threshold, and when said output current value is exceeding a point, at which the output voltage target value coincides with the predetermined constant voltage of the converter unit, and lower than the predetermined value; and wherein the converter unit includes a plurality of convertors (102a, 102b, 102c, 102d) connected in parallel and having a current share function based on a current share signal, and the output current value acquisition unit acquires the output current value of the converter unit by receiving the current share signal from the converter unit.