An apparatus for controlling an electric power output from a fuel cell in which a fuel gas and an oxidant gas are supplied to the fuel cell to generate the electric power output, the apparatus comprising: a controller for controlling operation of the fuel cell, the controller comprising: a memory portion; and an output characteristics learning portion; wherein the memory portion is adapted to store one or more base output characteristics of the fuel cell for each of a plurality of operating temperatures of fuel cell in the memory portion; the output characteristics learning portion is adapted to learn a relationship between one or more actual output characteristics of the fuel cell and the one or more base output characteristics stored in the memory portion for each of the plurality of operating temperatures; the controller is adapted to utilize the learned relationship between the one or more actual output characteristics and the one or more base characteristics in controlling operation of the fuel cell; and the one or more base output characteristics and the one or more actual output characteristics of the fuel cell include one or more of an output current, an output voltage, and an output power; characterized in that: the output characteristics learning portion is further adapted to: permitting learning only within a range of operating conditions where an input/output relationship of the fuel cell is stable; prohibiting learning when there is no change in an actual current for an operating condition of the fuel cell for more than a predetermined value in relation to a previously learned actual current at the operating condition; and prohibiting learning when an actual current is less than a first predetermined current or more than a second predetermined current, wherein the controller and the output characteristics learning portion are adapted to approximate a relationship between an actual current and the difference between an actual voltage and a base voltage as a linear function. a controller for controlling operation of the fuel cell, the controller comprising: a memory portion; and an output characteristics learning portion; wherein the memory portion is adapted to store one or more base output characteristics of the fuel cell for each of a plurality of operating temperatures of fuel cell in the memory portion; a memory portion; and an output characteristics learning portion; wherein the memory portion is adapted to store one or more base output characteristics of the fuel cell for each of a plurality of operating temperatures of fuel cell in the memory portion; the output characteristics learning portion is adapted to learn a relationship between one or more actual output characteristics of the fuel cell and the one or more base output characteristics stored in the memory portion for each of the plurality of operating temperatures; the controller is adapted to utilize the learned relationship between the one or more actual output characteristics and the one or more base characteristics in controlling operation of the fuel cell; and the one or more base output characteristics and the one or more actual output characteristics of the fuel cell include one or more of an output current, an output voltage, and an output power; characterized in that: the output characteristics learning portion is further adapted to: permitting learning only within a range of operating conditions where an input/output relationship of the fuel cell is stable; prohibiting learning when there is no change in an actual current for an operating condition of the fuel cell for more than a predetermined value in relation to a previously learned actual current at the operating condition; and prohibiting learning when an actual current is less than a first predetermined current or more than a second predetermined current, wherein the controller and the output characteristics learning portion are adapted to approximate a relationship between an actual current and the difference between an actual voltage and a base voltage as a linear function. the output characteristics learning portion is further adapted to: permitting learning only within a range of operating conditions where an input/output relationship of the fuel cell is stable; prohibiting learning when there is no change in an actual current for an operating condition of the fuel cell for more than a predetermined value in relation to a previously learned actual current at the operating condition; and prohibiting learning when an actual current is less than a first predetermined current or more than a second predetermined current, permitting learning only within a range of operating conditions where an input/output relationship of the fuel cell is stable; prohibiting learning when there is no change in an actual current for an operating condition of the fuel cell for more than a predetermined value in relation to a previously learned actual current at the operating condition; and prohibiting learning when an actual current is less than a first predetermined current or more than a second predetermined current, wherein the controller and the output characteristics learning portion are adapted to approximate a relationship between an actual current and the difference between an actual voltage and a base voltage as a linear function.