To provide a power supply system, capable of making efficient use of the electrical energy of a power supply.

This power supply system 200 comprises a power supply 210, a voltage-monitoring means 220 for detecting that the voltage of the power supply 210 becomes lower than the limit level for must-use, a usage limiting means 230 for limiting the use of the power supply 210, when the voltage of the power supply 210 becomes lower than the limit level for use, and a usage limitation prohibiting means 240 for limiting the usage limiting means 230 from limiting the use of the power supply 210, when the voltage of the power supply 210 becomes lower than the limit level for use, due to a temporary voltage drop which is different from the voltage drop corresponding the discharge curve of the power supply 210.