A plant performance evaluation apparatus (4, 4A) comprising: a first storage unit storing a first static model indicating a model of a first steady state in a plant, the first steady state indicating a state in which there is no change in input and output of process units included in the plant with time; a second storage unit storing a first dynamic model indicating a model of a dynamic state of the plant, the dynamic state indicating a state in which the input and output of the process units included in the plant vary with time; a model converter configured to convert the first dynamic model to a second static model indicating a model of a second steady state of the plant, the second steady state indicating a state in which there is no change in the input and output of the process units with time, and to store the second static model into the first storage unit, the first steady state indicating a steady state of the process units temporally before the second steady state characterized by: an operating condition equalizer configured to equalize the operating conditions of the process units at the time of generation of the first static model and the operating conditions of the process units at the time of generation of the second static model; a comparator configured to compare parameters included in equations indicating the first static model with parameters included in equations indicating the second static model and to output a comparison result; and a display configured to display the comparison result output from the comparator, wherein the model converter is configured to remove parameters varying with time included in equations indicating the first dynamic model or to make the parameters constant to convert the first dynamic model to the second static model, and the comparator is configured to compare the parameters included in the equations indicating the first static model with the parameters included in the equations indicating the second static model, the first static model and the second static model having been equalized by the operation condition equalizer, and to generate a comparison list that extracts parameters having a difference. a first storage unit storing a first static model indicating a model of a first steady state in a plant, the first steady state indicating a state in which there is no change in input and output of process units included in the plant with time; a second storage unit storing a first dynamic model indicating a model of a dynamic state of the plant, the dynamic state indicating a state in which the input and output of the process units included in the plant vary with time; a model converter configured to convert the first dynamic model to a second static model indicating a model of a second steady state of the plant, the second steady state indicating a state in which there is no change in the input and output of the process units with time, and to store the second static model into the first storage unit, the first steady state indicating a steady state of the process units temporally before the second steady state characterized by: an operating condition equalizer configured to equalize the operating conditions of the process units at the time of generation of the first static model and the operating conditions of the process units at the time of generation of the second static model; a comparator configured to compare parameters included in equations indicating the first static model with parameters included in equations indicating the second static model and to output a comparison result; and a display configured to display the comparison result output from the comparator, an operating condition equalizer configured to equalize the operating conditions of the process units at the time of generation of the first static model and the operating conditions of the process units at the time of generation of the second static model; a comparator configured to compare parameters included in equations indicating the first static model with parameters included in equations indicating the second static model and to output a comparison result; and a display configured to display the comparison result output from the comparator, wherein the model converter is configured to remove parameters varying with time included in equations indicating the first dynamic model or to make the parameters constant to convert the first dynamic model to the second static model, and the comparator is configured to compare the parameters included in the equations indicating the first static model with the parameters included in the equations indicating the second static model, the first static model and the second static model having been equalized by the operation condition equalizer, and to generate a comparison list that extracts parameters having a difference.