A plant control system controls a plant (E) modeled as a discrete-system model including an element relative to a response delay of the plant (E) and an element relative to a dead time of the plant (E). The plant control system includes an actuator (1) for generating an input (LAF) to the plant (E), a first detector (6) for detecting an output from the plant (E), and a second detector (5) for detecting the input to the plant (E). An estimator (26) generates data representing an estimated value (VO2) of an output of the first detector (6) after the dead time, based on data representing an output of the second detector (5). A manipulated variable determining unit (13) determines a manipulated variable (KCMD) which determines the input to the plant (E), based on the estimated value, represented by the data generated by the estimator, of the output of the first detector (6) after the dead time. The input to the plant (E) from the actuator (1) is controlled such that the output from the first detector (6) will be equalized to a predetermined target value.