A power supply system generates drive power and supplies the drive power to a load. The system includes an electric power generating part having at least a power generation section which has a fuel cell that generates electricity generation power by use of a power generation fuel. An external power supply connection section connects an external power supply supplying externally supplied power. An operation control section includes a section for setting the power generation section in a standby state on the basis of the externally supplied power supplied from the external power supply when at least the external power supply is connected to the external power supply connection section.