Provides a diagnostic apparatus for diagnosing a measured object based on time-series data of a plurality of parameters measured from the measured object. An example of an apparatus includes a change-point score calculating portion for calculating a time-series change-point score with which each of the plurality of parameters changes according to passage of time based on the time-series data on the parameter, a change-point correlation calculating portion for calculating a change-point correlation indicating strength by which each of the plurality of parameters is associated with each of other parameters based on the change-point scores of the parameter and the other parameter, and a parameter outputting portion for outputting a set of parameters of which calculated degrees of associations are higher than a predetermined reference change-point correlation as a set of mutually strongly associated parameters.