An operation management device includes: an information collection module which collects, from a managed device, first and second performance information showing a time series change in the performance information; a correlation model generation module which derives a correlation function between the first and second performance information and creates a correlation model based on the correlation function; a correlation change analysis module which judges whether or not the current first and second performance information acquired by the information collection module satisfy the relation shown by the conversion function between the first and second performance information of the correlation model within a specific error range; and a failure period extraction module which, when the first and second performance information does not satisfy the relation shown by the conversion function of the correlation model, extracts a period of that state as a failure period.