An automatic analyzer for performing analysis of a precision control sample in response to an external factor to alleviate the burden on the operator and perform precision control at appropriate timing, thereby allowing automatic maintenance of the measurement precision. Analysis of a precision control sample is performed by creating an analysis request for the internally held precision control sample and then transferring the precision control sample in response to an external factor occurring, when a calibrator is inputted in the analyzer, the number of remaining reagents under analysis satisfies a predetermined condition (becomes zero or falls below a specified value), the date changes, a specified time runs out, the operator is changed, the number of analyzed samples exceeds a specified value, a specified time period has elapsed, a new reagent is registered, and a measurement failure is detected.