An automated analyzer maintains high processing capacity and dispensation accuracy even when items requiring dilution/pretreatment and general reaction measurement are mixed. A plurality of sample dispensing mechanisms are independently driven and each include a sample collection position, a sample nozzle for collecting the sample, and a washing tank for washing the sample nozzle. The sample dispensing mechanisms are configured to collect the sample from a plurality of sample collection positions and are operated independently to perform sample dispensation into reaction containers on a reaction disc. At least one of the sample dispensing mechanisms is provided for each of a sample requiring dilution/pretreatment and a sample that does not require dilution/pretreatment. The automated analyzer is provided with a control means for causing the respective mechanisms to be operated in a dedicated manner. The sample is dispensed such that no vacancy is created in the reaction containers.