An automatic analyzer is capable of ensuring sufficient nozzle cleaning and suppressing of deterioration in the accuracy of analysis. When it is judged that there remains no analysis item of the sample, a judgment is made on whether the sample dispensation quantity of the n-th sample dispensation is less than a dispensation quantity threshold value or not, and if less, a cleaning pattern is selected by making a judgment on whether or not all the sample dispensation quantities of the first through (n−1)-th sample dispensations are less than the dispensation quantity threshold value. If the sample dispensation quantity of the n-th sample dispensation is the dispensation quantity threshold value or more, another cleaning pattern selected by making the judgment on whether or not all the sample dispensation quantities of the first through (n−1)-th sample dispensations are less than the dispensation quantity threshold value.