An automatic analyzer comprising: a rotatable reaction disk having a plurality of reaction cells arranged circumferentially thereon, each of the reaction cells being for mixing and reacting a sample and a reagent with each other therein; a sample dispensing mechanism that is configured to dispense samples to the reaction cells arranged on the reaction disk and to dispense samples to a disposable reaction vessel located at a coagulation time sample dispensing position outside of the reaction disk; a first reagent dispensing mechanism that is configured to dispense reagents to the reaction cells arranged on the reaction disk; a light source configured to irradiate a reaction solution including one of the samples and one of the reagents in the reaction cells with light; a photometer arranged opposite to the light source and configured to detect transmitted light or scattered light from the reaction solution; a reaction cell cleaning mechanism configured to clean the reaction cells; a blood coagulation time measuring section that includes a temperature-regulating block which has a plurality of coagulation time detecting parts, the blood coagulation time measuring section being configured to irradiate a reaction solution in the disposable reaction vessel with light to thereby detect transmitted light or scattered light; a reaction vessel transfer mechanism configured to move the disposable reaction vessel from the coagulation time sample dispensing position to one of the coagulation time detecting parts; Characterized in that it further comprises: a second reagent dispensing mechanism with a reagent heating function configured to suction one of the reagents from the reaction cells and to dispense the suctioned reagent to the disposable reaction vessel at the one of the coagulation time detecting parts; and a controller configured to control the reaction disk, the blood coagulation time measuring section, and the first reagent dispensing mechanism so that at a timing at which a sample is dispensed to the coagulation time sample dispensing position, the reaction disk rotates without the sample being dispensed to the reaction cell to thereby produce an empty reaction cell, and then the first reagent dispensing mechanism dispenses the reagents to the empty reaction cell. a rotatable reaction disk having a plurality of reaction cells arranged circumferentially thereon, each of the reaction cells being for mixing and reacting a sample and a reagent with each other therein; a sample dispensing mechanism that is configured to dispense samples to the reaction cells arranged on the reaction disk and to dispense samples to a disposable reaction vessel located at a coagulation time sample dispensing position outside of the reaction disk; a first reagent dispensing mechanism that is configured to dispense reagents to the reaction cells arranged on the reaction disk; a light source configured to irradiate a reaction solution including one of the samples and one of the reagents in the reaction cells with light; a photometer arranged opposite to the light source and configured to detect transmitted light or scattered light from the reaction solution; a reaction cell cleaning mechanism configured to clean the reaction cells; a blood coagulation time measuring section that includes a temperature-regulating block which has a plurality of coagulation time detecting parts, the blood coagulation time measuring section being configured to irradiate a reaction solution in the disposable reaction vessel with light to thereby detect transmitted light or scattered light; a reaction vessel transfer mechanism configured to move the disposable reaction vessel from the coagulation time sample dispensing position to one of the coagulation time detecting parts; Characterized in that it further comprises: a second reagent dispensing mechanism with a reagent heating function configured to suction one of the reagents from the reaction cells and to dispense the suctioned reagent to the disposable reaction vessel at the one of the coagulation time detecting parts; and a controller configured to control the reaction disk, the blood coagulation time measuring section, and the first reagent dispensing mechanism so that at a timing at which a sample is dispensed to the coagulation time sample dispensing position, the reaction disk rotates without the sample being dispensed to the reaction cell to thereby produce an empty reaction cell, and then the first reagent dispensing mechanism dispenses the reagents to the empty reaction cell. a second reagent dispensing mechanism with a reagent heating function configured to suction one of the reagents from the reaction cells and to dispense the suctioned reagent to the disposable reaction vessel at the one of the coagulation time detecting parts; and a controller configured to control the reaction disk, the blood coagulation time measuring section, and the first reagent dispensing mechanism so that at a timing at which a sample is dispensed to the coagulation time sample dispensing position, the reaction disk rotates without the sample being dispensed to the reaction cell to thereby produce an empty reaction cell, and then the first reagent dispensing mechanism dispenses the reagents to the empty reaction cell.