A monitoring system includes a real-time detection device configured to detect a state of target equipment and an instruction output from a central control device configured to input a control instruction to the target equipment; and a monitoring device configured to acquire information from the real-time detection device. The monitoring device includes an analysis unit configured to simulate the state of the target equipment, with models of the target equipment and the central control device, and a determination unit configured to determine whether an abnormality has occurred in the target equipment. The analysis unit is configured to simulate the state of the target equipment, using the latest information detected by the real-time detection device. The determination unit is configured to compare a result calculated by the analysis unit using the latest information detected by the real-time detection device.