A specimen loading or storing unit, comprising: a plurality of types of specimen trays, each configured to have a different size and provided with a plurality of specimen container installation parts for holding a specimen container; a specimen container transferring mechanism configured to transfer the specimen container between a conveyance line and the specimen tray; a specimen tray installation part configured to install the plurality of types of specimen trays; and a plurality of identification information readers arranged directly under the specimen tray installation part and configured to read information for identifying a type of specimen tray from a single identification information tag attached to each specimen tray; wherein each identification information tag is readable, when the identification information tag is positioned within a predetermined distance range from any one of the identification information readers; wherein the specimen loading or storing unit is adapted to determine a position where any one of the specimen trays is arranged based upon a combination of successful or unsuccessful reading attempts of the plurality of identification information readers, and characterized in that: the plurality of the specimen container installation parts are arranged to achieve a relationship which is p1>d1+d2 and p2>d3+d4, when d1 is set as a distance from a first side surface of the specimen tray to the center of a specimen container installation part which is most closely adjacent to the first side surface, d2 is set as a distance from a second side surface of the specimen tray opposite to the first side surface of the specimen tray to the center of a specimen container installation part which is most closely adjacent to the second side surface, p1 is set as a distance in a direction perpendicular to the first side surface and the second side surface between the center of two adjacent specimen container installation parts, d3 is set as a distance from a third side surface of the specimen tray to the center of a specimen container installation part which is most closely adjacent to the third side surface, d4 is set as a distance from a fourth side surface opposite to the third side surface of the specimen tray to the center of a specimen container installation part which is most closely adjacent to the fourth side surface, and p2 is set as a distance in a direction perpendicular to the third side surface and the fourth side surface between the center of two adjacent specimen container installation parts. a plurality of types of specimen trays, each configured to have a different size and provided with a plurality of specimen container installation parts for holding a specimen container; a specimen container transferring mechanism configured to transfer the specimen container between a conveyance line and the specimen tray; a specimen tray installation part configured to install the plurality of types of specimen trays; and a plurality of identification information readers arranged directly under the specimen tray installation part and configured to read information for identifying a type of specimen tray from a single identification information tag attached to each specimen tray; wherein each identification information tag is readable, when the identification information tag is positioned within a predetermined distance range from any one of the identification information readers; wherein the specimen loading or storing unit is adapted to determine a position where any one of the specimen trays is arranged based upon a combination of successful or unsuccessful reading attempts of the plurality of identification information readers, and when d1 is set as a distance from a first side surface of the specimen tray to the center of a specimen container installation part which is most closely adjacent to the first side surface, d2 is set as a distance from a second side surface of the specimen tray opposite to the first side surface of the specimen tray to the center of a specimen container installation part which is most closely adjacent to the second side surface, p1 is set as a distance in a direction perpendicular to the first side surface and the second side surface between the center of two adjacent specimen container installation parts, d3 is set as a distance from a third side surface of the specimen tray to the center of a specimen container installation part which is most closely adjacent to the third side surface, d4 is set as a distance from a fourth side surface opposite to the third side surface of the specimen tray to the center of a specimen container installation part which is most closely adjacent to the fourth side surface, and p2 is set as a distance in a direction perpendicular to the third side surface and the fourth side surface between the center of two adjacent specimen container installation parts.