PLANT EVALUATION DEVICE AND PLANT EVALUATION METHOD

In order to estimate the cause of an abnormality occurring in a plant in an efficient manner, this plant evaluation device (5) is equipped with: a first calculation unit (52) that uses a steady model to calculate a first estimated value for a plant state amount, calculates equipment parameters for the plant equipment in accordance with the difference between the first estimated value and an actual measured value for the plant state amount, and saves the calculated equipment parameters as normal-state equipment parameters; a first determination unit (53) that uses an unsteady model to calculate a second estimated value for the plant state amount, and that determines whether the error between the second estimated value and the actual measured value is equal to or greater than a given threshold value; a second calculation unit (54) that uses the steady model to calculate a third estimated value for the plant state amount in accordance with the determination result from the first determination unit, calculates the equipment parameters in accordance with the difference between the third estimated value and the actual measured value, and saves the calculated equipment parameters as abnormal-state equipment parameters; and a second determination unit (55) that determines whether the difference between the normal-state equipment parameters and the abnormal-state equipment parameters is equal to or greater than a fixed value.