A plant monitoring and control apparatus having a function to simulate an object to be monitored and controlled for verifying healthiness of a control processing unit is provided with an input separating operation unit and an output separating operation unit which separate DI data and DO data handled by the control processing unit by transforming the DI data and the DO data into a label format differing from a label format of PDI data and PDO data which are related to input and output between the object to be monitored and controlled and the plant monitoring and control apparatus. In test mode, a switching unit switches an input device of the control processing unit and an output device thereof to a simulator unit provided within the plant monitoring and control apparatus.