An automatic analyzer including a function for operating control materials and its operation method are provided. The analyzer is configured to start sampling by giving priority to an entirety of control materials corresponding to all assay items required for measurement. The analyzer is also configured to automatically start sampling of a patient specimen based on a preliminarily set sampling timing after completion of sampling of the entirety of control materials. The analyzer is also configured to stop, when an abnormality is present in a measurement result of at least any one of control materials in the group of control materials, sampling of a patient specimen corresponding to a control material in which the abnormality is found, and notify a tester of the abnormality.