A signal reference value (SLocal) is set at which a blood coagulation reaction time (T) of a blood coagulation time reference sample measured on the basis of the result of comparing a signal value (amount of transmitted light, amount of scattered light, amount of fluorescence, or turbidity) pertaining to blood coagulation time that varies temporally according to the mixing and reaction of the blood coagulation time reference sample and a reagent and a signal reference value (S) corresponds to an expected value (Te) for the blood coagulation reaction time that has been set beforehand so as to correspond to the blood coagulation time reference sample. As a result, it is possible to use the blood coagulation time reference sample to determine the state of the reagent and enhance the reliability of measurement results by setting a unique signal reference value for each reagent container.