An automatic analysis device comprising: a plurality of specimen containers; a specimen dispensing mechanism; a reaction container; a reagent dispensing mechanism configured to dispense a reagent to the reaction container; and a measurement unit configured to irradiate blood plasma to which the reagent was added inside the reaction container with light emitted from a light source, and to measure the coagulation time, based on obtained scattered light and/or transmitted light, characterised in that the plurality of specimen containers include a vacant specimen container, wherein the specimen dispensing mechanism is configured to dispense subject blood plasma and normal blood plasma to be added to correct a coagulation time of the subject blood plasma, to the vacant specimen container, the specimen dispensing mechanism is further configured to dispense the subject blood plasma alone, the normal blood plasma alone, and mixed blood plasma obtained by mixing the subject blood plasma and the normal blood plasma at least at one mixing ratio prepared inside the specimen container, each into a said reaction container, a control unit is configured to control the specimen dispensing mechanism to dispense the prepared subject blood plasma, normal blood plasma, and mixed blood plasma from the specimen container each to a said reaction container immediately for immediate coagulation reaction time measurement to be carried out and, thereafter, to control the specimen dispensing mechanism to dispense a remaining specimen of the prepared mixed blood plasma to a said reaction container after the specimen container containing the remaining specimen has been incubated at 37°C in an incubator for a predetermined period of time, for delayed coagulation reaction time measurement to be carried out, and the measurement unit is configured to irradiate the subject blood plasma to which the reagent inside the reaction container is added, the normal blood plasma and the mixed blood plasma with light emitted from a light source to measure the coagulation time. a plurality of specimen containers; a specimen dispensing mechanism; a reaction container; a reagent dispensing mechanism configured to dispense a reagent to the reaction container; and a measurement unit configured to irradiate blood plasma to which the reagent was added inside the reaction container with light emitted from a light source, and to measure the coagulation time, based on obtained scattered light and/or transmitted light, characterised in that the plurality of specimen containers include a vacant specimen container, wherein the specimen dispensing mechanism is configured to dispense subject blood plasma and normal blood plasma to be added to correct a coagulation time of the subject blood plasma, to the vacant specimen container, the specimen dispensing mechanism is further configured to dispense the subject blood plasma alone, the normal blood plasma alone, and mixed blood plasma obtained by mixing the subject blood plasma and the normal blood plasma at least at one mixing ratio prepared inside the specimen container, each into a said reaction container, a control unit is configured to control the specimen dispensing mechanism to dispense the prepared subject blood plasma, normal blood plasma, and mixed blood plasma from the specimen container each to a said reaction container immediately for immediate coagulation reaction time measurement to be carried out and, thereafter, to control the specimen dispensing mechanism to dispense a remaining specimen of the prepared mixed blood plasma to a said reaction container after the specimen container containing the remaining specimen has been incubated at 37°C in an incubator for a predetermined period of time, for delayed coagulation reaction time measurement to be carried out, and the measurement unit is configured to irradiate the subject blood plasma to which the reagent inside the reaction container is added, the normal blood plasma and the mixed blood plasma with light emitted from a light source to measure the coagulation time.