Provided is a diagnostic apparatus easily applied to diagnosis of a small lot product, etc. When measurement data on a measurement object is inputted sequentially, a filter section (408) performs filtering of the measurement data. When new measurement data is employed as diagnosis object data, a statistic processing section (420) updates diagnosis reference data using the new diagnosis object data. A diagnostic section (416) diagnoses the diagnosis object data based on the diagnosis reference data and determines whether an abnormality is present or not. If an abnormality is present, the fact is displayed to a user along with diagnosis results through an UI section (428).