1. An operations management apparatus which acquires performance information for each of a plurality of performance items from a plurality of controlled units and manages operation of the controlled units, comprising: a correlation model generation unit which derives, when the performance items or the controlled units are designated as an element of performance information, a correlation function between a first series of performance information that indicates time series variation about a first element and a second series of performance information that indicates time series variation about a second element, generates a correlation model between the first element and the second element based on the correlation function, and obtains the correlation model for each element pair of the performance information; and a correlation change analysis unit which analyzes a change in the correlation model based on the performance information acquired newly which has not been used for generation of the correlation model.