A rack buffer unit 8 serving as a sample-container switching unit is provided between a rack conveying module 4 and a rack conveying module 5 which convey racks 2 on which the sample containers 1 are mounted, and an urgent-sample loading module 7 installing a rack 2 on which a sample container 1 storing a sample desired to be preferentially analyzed is mounted is provided. The rack 2 which is in the process of sample dispensing and the rack 2 desired to be preferentially analyzed are switched from each other by the rack buffer unit 8, and the sample container 1 mounted on the rack 2 desired to be preferentially analyzed is moved to a sample dispensing position in a short period of time.