A control apparatus for electric power plant comprises turbine speed control means for detecting the speed of a turbine coupled to an electric generator to control the turbine speed by controlling a steam flow supplied to the turbine on the basis of the detected speed, pressure control means for controlling the pressure in a steam generator on the basis of the pressure of the steam generator, and correcting means for correcting the steam flow supplied to the turbine only when fluctuation in the pressure of the steam generator brought about by rapid change of a set load value is deviated from a predetermined range in which the steam pressure is allowed to vary, the correction of the steam flow being made in correspondence to the deviation.