An automatic analysis device, comprising: a reagent supply nozzle for transferring a reagent to a measurement portion, a reagent container holding portion that is configured to exchangeably hold a reagent container accommodating the reagent; a first flow path that is configured to supply the reagent in the reagent container to the measurement portion through the reagent supply nozzle; a second flow path that is disposed by being branched from the first flow path and can store a portion of the reagent in the reagent container; a reagent container side electromagnetic valve and a reagent supply nozzle side electromagnetic valve that are provided on the first flow path; liquid sending means for sending the reagent to the measurement portion and the reagent storage flow path by applying a negative pressure or positive pressure to the first flow path and the second flow path, wherein the liquid sending means are connected to the first flow path between the reagent container side electromagnetic valve and the reagent supply nozzle side electromagnetic valve; a reagent storage flow path side electromagnetic valve that is provided on the second flow path; wherein the reagent container side electromagnetic valve is positioned before a point where the second flow path is branched from the first flow path, and the reagent supply nozzle side electromagnetic valve is positioned after said point and the reagent supply nozzle is positioned after the reagent supply nozzle side electromagnetic valve, the automatic analysis device characterized by control means for controlling the reagent container side electromagnetic valve, the reagent storage flow path side electromagnetic valve, the reagent supply nozzle side electromagnetic valve and the liquid sending means so that a supply source, which is either the reagent container or the second flow path and which supplies a reagent to the measurement portion at a predetermined timing, is switched from the reagent container to the second flow path, and for controlling the reagent container side electromagnetic valve, the reagent storage flow path side electromagnetic valve, the reagent supply nozzle side electromagnetic valve and the liquid sending means in order to store a reagent, supplied from the reagent container, to the second flow path when detecting a predetermined trigger. a reagent supply nozzle for transferring a reagent to a measurement portion, a reagent container holding portion that is configured to exchangeably hold a reagent container accommodating the reagent; a first flow path that is configured to supply the reagent in the reagent container to the measurement portion through the reagent supply nozzle; a second flow path that is disposed by being branched from the first flow path and can store a portion of the reagent in the reagent container; a reagent container side electromagnetic valve and a reagent supply nozzle side electromagnetic valve that are provided on the first flow path; liquid sending means for sending the reagent to the measurement portion and the reagent storage flow path by applying a negative pressure or positive pressure to the first flow path and the second flow path, wherein the liquid sending means are connected to the first flow path between the reagent container side electromagnetic valve and the reagent supply nozzle side electromagnetic valve; a reagent storage flow path side electromagnetic valve that is provided on the second flow path; wherein the reagent container side electromagnetic valve is positioned before a point where the second flow path is branched from the first flow path, and the reagent supply nozzle side electromagnetic valve is positioned after said point and the reagent supply nozzle is positioned after the reagent supply nozzle side electromagnetic valve, the automatic analysis device characterized by control means for controlling the reagent container side electromagnetic valve, the reagent storage flow path side electromagnetic valve, the reagent supply nozzle side electromagnetic valve and the liquid sending means so that a supply source, which is either the reagent container or the second flow path and which supplies a reagent to the measurement portion at a predetermined timing, is switched from the reagent container to the second flow path, and for controlling the reagent container side electromagnetic valve, the reagent storage flow path side electromagnetic valve, the reagent supply nozzle side electromagnetic valve and the liquid sending means in order to store a reagent, supplied from the reagent container, to the second flow path when detecting a predetermined trigger.