<p>Provided is a diagnostic equipment for selecting data items to be used for diagnosis on the basis of the operation history information of an operator. The plant diagnostic equipment receives the measurement signal of a plant and the operation signal of the time when an operation is performed by the operator using an external input device and displays the state of the plant on an image display device as display information. The plant diagnostic equipment has a measurement signal database for storing the measurement signal of the plant, an operation history database for storing the operation signal of the time when the operation is performed by the operator using the external input device, and a learning means for extracting a data item to be used for the diagnosis of the plant from the display information displayed on the image display device by the operation performed by the operator using the external input device when an abnormality in the plant occurs.</p>
