A power supply unit in a hybrid structure of a fuel cell and a power storage unit and a control method for the power supply unit, in which a small-size light-weight power storage unit is used and chances of incomplete functioning have been eliminated. In addition to the downsizing of the power storage unit and a reduction of the system price, it also becomes possible to start the fuel cell at high speed and raise the fuel cell temperature quickly, monitor output and remaining mounts of fuel and power, and take measures against fluctuations of output, and provides immediate availability of portable devices like the ones using a conventional secondary cell.