Abstract: A data checking apparatus receives and checks observation data on a plurality of observation items including first and second observation items. The observation data is obtained by analyzing a single object with a plurality of analyzers including first and second analyzers. The apparatus includes an input device for inputting, beforehand, correlation data indicating correlation among the plurality of observation items, a memory for storing the input correlation data, a judgment device for cross-checking the observation data on the plurality of items to judge as to whether the received observation data conforms to the stored correlation data, and an output device for outputting results of the judgment.