There is provided an apparatus, including a first storage storing first time-series data including instruction values given to first to K-th control devices and measured values from first to K-th sensors during a first period, a model optimizer, for each of combinations of two of the control devices, generating a diagnostic model instance of a predetermined target model and obtaining an optimized diagnostic model instance in which parameters of the diagnostic mode instance are identified, a second storage storing second time-series data acquired during a second period, a calculator, for each of the optimized diagnostic model instances, calculating a determination score for each of the control devices and sensors using the first and second time-series data, and a determiner determining presence or absence of an abnormality for each of the control devices and the sensors based on each determination score.