An automatic analysis device comprising: a dispensing probe having a cylindrical shape and configured to dispense a reagent to a reaction vessel to which a sample is dispensed; and a control device configured to control the dispensing probe, wherein the control device is configured to control the dispensing probe to execute an aspiration step of aspirating the reagent from a reagent vessel that stores the reagent; a first dispensing and aspiration step of dispensing a first liquid amount (Va) of the reagent aspirated from the reagent vessel in the aspiration step to the reaction vessel and aspirating, from the reaction vessel, a second liquid amount (Vb) of a mixed liquid obtained by mixing the reagent and the sample in the reaction vessel; a second dispensing and aspiration step, after the first dispensing and aspiration step, of dispensing a third liquid amount (Vc) of mixed liquid aspirated from the reaction vessel and the reagent aspirated in the aspiration step and remaining in the dispensing probe to the reaction vessel and aspirating a fourth liquid amount (Vd) of the mixed liquid from the reaction vessel; and a final dispensing step, after the second dispensing and aspiration step, of dispensing mixed liquid aspirated from the reaction vessel and the reagent aspirated in the aspiration step and remaining in the dispensing probe in a predetermined dispensing amount (Vdil), wherein the first liquid amount (Va) is less than the third liquid amount (Vc), and the third liquid amount (Vc) is less than the predetermined dispensing amount (Vdil). a dispensing probe having a cylindrical shape and configured to dispense a reagent to a reaction vessel to which a sample is dispensed; and a control device configured to control the dispensing probe, wherein the control device is configured to control the dispensing probe to execute an aspiration step of aspirating the reagent from a reagent vessel that stores the reagent; a first dispensing and aspiration step of dispensing a first liquid amount (Va) of the reagent aspirated from the reagent vessel in the aspiration step to the reaction vessel and aspirating, from the reaction vessel, a second liquid amount (Vb) of a mixed liquid obtained by mixing the reagent and the sample in the reaction vessel; a second dispensing and aspiration step, after the first dispensing and aspiration step, of dispensing a third liquid amount (Vc) of mixed liquid aspirated from the reaction vessel and the reagent aspirated in the aspiration step and remaining in the dispensing probe to the reaction vessel and aspirating a fourth liquid amount (Vd) of the mixed liquid from the reaction vessel; and a final dispensing step, after the second dispensing and aspiration step, of dispensing mixed liquid aspirated from the reaction vessel and the reagent aspirated in the aspiration step and remaining in the dispensing probe in a predetermined dispensing amount (Vdil), wherein the first liquid amount (Va) is less than the third liquid amount (Vc), and the third liquid amount (Vc) is less than the predetermined dispensing amount (Vdil). an aspiration step of aspirating the reagent from a reagent vessel that stores the reagent; a first dispensing and aspiration step of dispensing a first liquid amount (Va) of the reagent aspirated from the reagent vessel in the aspiration step to the reaction vessel and aspirating, from the reaction vessel, a second liquid amount (Vb) of a mixed liquid obtained by mixing the reagent and the sample in the reaction vessel; a second dispensing and aspiration step, after the first dispensing and aspiration step, of dispensing a third liquid amount (Vc) of mixed liquid aspirated from the reaction vessel and the reagent aspirated in the aspiration step and remaining in the dispensing probe to the reaction vessel and aspirating a fourth liquid amount (Vd) of the mixed liquid from the reaction vessel; and a final dispensing step, after the second dispensing and aspiration step, of dispensing mixed liquid aspirated from the reaction vessel and the reagent aspirated in the aspiration step and remaining in the dispensing probe in a predetermined dispensing amount (Vdil), wherein the first liquid amount (Va) is less than the third liquid amount (Vc), and the third liquid amount (Vc) is less than the predetermined dispensing amount (Vdil).