The objective of the present disclosure is to provide a technique for reducing a quantity of magnetic particles remaining on a reaction vessel wall surface in a cleaning step for reducing, in a stepwise manner, an amount of a magnetic particle solution in the reaction vessel. The automated analysis device according to the present disclosure causes an agitating mechanism to operate in such a way that a magnetic substance remaining on the wall surface of the vessel in the previous cleaning step is captured by a cleaning solution in the next cleaning step.