An output controlling apparatus of an energy storage apparatus for a reliability of an output of a photovoltaic power generation is provided. The output controlling apparatus includes a power generation amount predictor configured to predict a next day's power generation amount of a photovoltaic power generator, a target output generator configured to determine a target output based on a charging state of an energy storage apparatus used for a photovoltaic power generation, a real-time output criterion generator configured to generate an output criterion used for outputs from the photovoltaic power generator and the energy storage apparatus to a system in units of time based on the target output and the charging state of the energy storage apparatus, and a charging/discharging controller configured to control charging and discharging of the energy storage apparatus such that an output to the system follows the output criterion.