In a large-scale plant such as a power plant, a graphical user interface device displays a target data display screen without increasing a load of searching a screen or a load of grasping a screen transition link. An operation model-creating device reads operation manual data for operation estimation and operation history data from an operation manual managing device and an operation history managing device to create a number of pieces of manual procedure template data for each accident type. An operation predicting device selects the operation procedure template data having same conditions of immediately preceding operation history data obtained from the plant monitoring and control device to predict the next operation estimated to be performed by an operator from the selected operation procedure template data. The plant monitoring and control device displays a system recommended operation button on a monitoring screen thereof based on data of the predicted results.