An automatic in vitro diagnostic apparatus comprising: a base frame; a cuvette tray movable back and forth on the base frame, for mounting cuvette holders thereon, the cuvette holders accommodating a plurality of cuvettes arranged alongside each other, wherein each cuvette includes at least one open chamber, a reagent chamber, a tip, and a cartridge comprising an assay strip; and a first driving unit for moving the cuvette tray back and forth; a sampling operation unit movable left and right perpendicular to the moving direction of the cuvette tray on the base frame; a third driving unit for moving the sampling operation unit left and right; an optical analysis unit disposed at the rear end of the sampling operation unit, movable left and right on the base frame, for optically analyzing the assay strip of the cuvette; wherein the term moving direction describes the front-rear direction with respect to the horizontal plane in which the cuvette tray is located, and the direction perpendicular to the moving direction describes the left-right direction, a fourth driving unit for moving the optical analysis unit left and right; characterized in that the automatic in vitro diagnostic apparatus further comprises a tube tray movable back and forth in parallel with the moving direction of the cuvette tray on the base frame, for mounting tube holders thereon, the tube holders accommodating a plurality of capless sample tubes containing samples; a second driving unit for moving the tube tray back and forth; and a control unit for controlling the automatic in vitro diagnostic apparatus and configured to cause the sampling operation unit to collect a sample contained in one of said sample tubes accommodated on a tube holder mounted on said tube tray, mixing it in an open chamber of a cuvette accommodated in a cuvette holder mounted on said cuvette tray with a reagent taken from a reagent chamber of said cuvette, and dropping the mixed solution in the open chamber onto the assay strip provided in said cuvette. a base frame; a cuvette tray movable back and forth on the base frame, for mounting cuvette holders thereon, the cuvette holders accommodating a plurality of cuvettes arranged alongside each other, wherein each cuvette includes at least one open chamber, a reagent chamber, a tip, and a cartridge comprising an assay strip; and a first driving unit for moving the cuvette tray back and forth; a sampling operation unit movable left and right perpendicular to the moving direction of the cuvette tray on the base frame; a third driving unit for moving the sampling operation unit left and right; an optical analysis unit disposed at the rear end of the sampling operation unit, movable left and right on the base frame, for optically analyzing the assay strip of the cuvette; wherein the term moving direction describes the front-rear direction with respect to the horizontal plane in which the cuvette tray is located, and the direction perpendicular to the moving direction describes the left-right direction, a fourth driving unit for moving the optical analysis unit left and right; characterized in that the automatic in vitro diagnostic apparatus further comprises a tube tray movable back and forth in parallel with the moving direction of the cuvette tray on the base frame, for mounting tube holders thereon, the tube holders accommodating a plurality of capless sample tubes containing samples; a second driving unit for moving the tube tray back and forth; and a control unit for controlling the automatic in vitro diagnostic apparatus and configured to cause the sampling operation unit to collect a sample contained in one of said sample tubes accommodated on a tube holder mounted on said tube tray, mixing it in an open chamber of a cuvette accommodated in a cuvette holder mounted on said cuvette tray with a reagent taken from a reagent chamber of said cuvette, and dropping the mixed solution in the open chamber onto the assay strip provided in said cuvette.