An automatic analyzer, comprising: a dispensing unit configured to dispense a sample and/or a reagent into a reaction vessel; a reaction unit configured to perform an incubation and a bound-free separation for reactants in the reaction vessel; a measuring unit independent of the reaction unit and configured to measure a reaction signal in the reaction vessel; and a transfer unit configured to transfer the reaction vessel between different positions; wherein the reaction unit comprises a rotation device provided with a reaction vessel holder for holding the reaction vessel; the rotation device is a reaction carousel configured to rotate by a fixed angle at a fixed interval so as to carry the reaction vessel holder of the reaction carousel forward; wherein the measuring unit comprises a measurement carousel provided with a reaction vessel holder for holding the reaction vessel, the reaction vessel holder of the measurement carousel is further provided with a dispensing position to perform the dispensing of the sample and/or the reagent; at least one reaction vessel holder of the reaction carousel and at least one reaction vessel holder of the measurement carousel are in a horizontal movable area of the transfer unit; wherein the reaction vessel holder of the reaction carousel comprises a first reaction vessel holder configured to transfer the reaction vessel for a bound-free separation and a second reaction vessel holder (11a, 11b, 11c) configured to perform an incubation for the reactants in the reaction vessel; wherein the transfer unit is configured to transfer the reaction vessel among a reaction vessel supply unit, the first reaction vessel holder of the reaction carousel, the second reaction vessel holder of the reaction carousel, the reaction vessel holder of the measurement carousel, and a reaction vessel disposal chute. a dispensing unit configured to dispense a sample and/or a reagent into a reaction vessel; a reaction unit configured to perform an incubation and a bound-free separation for reactants in the reaction vessel; a measuring unit independent of the reaction unit and configured to measure a reaction signal in the reaction vessel; and a transfer unit configured to transfer the reaction vessel between different positions; wherein the reaction unit comprises a rotation device provided with a reaction vessel holder for holding the reaction vessel; the rotation device is a reaction carousel configured to rotate by a fixed angle at a fixed interval so as to carry the reaction vessel holder of the reaction carousel forward; wherein the measuring unit comprises a measurement carousel provided with a reaction vessel holder for holding the reaction vessel, the reaction vessel holder of the measurement carousel is further provided with a dispensing position to perform the dispensing of the sample and/or the reagent; at least one reaction vessel holder of the reaction carousel and at least one reaction vessel holder of the measurement carousel are in a horizontal movable area of the transfer unit; wherein the reaction vessel holder of the reaction carousel comprises a first reaction vessel holder configured to transfer the reaction vessel for a bound-free separation and a second reaction vessel holder (11a, 11b, 11c) configured to perform an incubation for the reactants in the reaction vessel; wherein the transfer unit is configured to transfer the reaction vessel among a reaction vessel supply unit, the first reaction vessel holder of the reaction carousel, the second reaction vessel holder of the reaction carousel, the reaction vessel holder of the measurement carousel, and a reaction vessel disposal chute.