Provided is a technology that monitors sensors themselves and prevents misdiagnosis caused by deterioration over time and environmental changes. This sensor monitoring device provided in power plants comprises: a plurality of sensor sets each including a plurality of sensors; a database that models the correlation between sensor values from the plurality of sensors configuring each sensor set and the sensor values from a plurality of sensors configuring other sensor sets, and stores same as a relationship model; and a correlation detection module. The correlation detection module: compares the correlation between the sensor detection values for the plurality of sensors configuring each sensor set and the sensor detection values for the plurality of sensors configuring the other sensor sets, and the correlation to the modeled relationship model stored in the database, and detects deviation from the correlation to the modeled relationship model, in the correlation between the detected sensor values.
