1. An error detection method for early detection of errors in a plant or facilities, comprising of steps of: acquiring data from a plurality of sensors; dividing a trace in a data space into a plurality of clusters over time on the basis of a temporal change of the data; wherein a trace in a data space represents the sensor data acquired over a period of time; wherein a data space represents attributes of sensor data; wherein each cluster corresponds to an operation state of the plant or facilities; for each operation state, modeling the corresponding divided clusters by a sub space method; and calculating a discrepancy value based on the models of derived clusters as an error candidate.