A control device and method for a fuel cell system accurately learns output characteristics of fuel cell even when the output characteristics of fuel cell change due to changes in fuel cell temperature. The method and device generate power by supplying fuel and oxidant gases. The control device has a memory portion that memorizes output characteristics of fuel cell that change with the temperatures of fuel cell, and that become the base output characteristics, for each of the temperatures. An output characteristics learning portion learns the relationship between the output characteristics that become the base output characteristics and the actual output characteristics of fuel cell. The output characteristics learning portion prohibits learning when an actual current is less than a first predetermined current and more than a second predetermined current.