A plant control device according to the present invention includes a feedback controller and a reference governor. The feedback controller is configured to determine a control input of a plant by feedback control so as to bring an output value of a control amount of the plant close to a target value. The reference governor is configured to calculate a future predicted value of a specific state quantity of the plant by using a model of a closed loop system including the plant and the feedback controller, and correct the target value that is given to the feedback controller based on the predicted value of the specific state quantity and a constraint that is imposed on the specific state quantity.