the same manner as that explained in connection with the reaction curve b in this case all the absorbance values within the monitor section are smaller than max od and larger than min od just as in the case of the reaction curve h then it is judged whether or not the absorbance differences within the monitor section is positive in this case 34 yes 34 judgement is given then it is checked whether or not an absolute value of an absorbance difference between the primary data use start and end points t 5 and t 14 is larger than a predetermined value u03b1 the value u03b1 may be set to a relatively small value such as 0 001 to 0 002 when a result of this judgement is 34 yes 34 the abnormality is determined then no more calculation is effected and only the abnormal mark is printed out contrary to this when it is determined that the above mentioned absolute value of the absorbance difference u03b4od is smaller than u03b1 a concentration or activity value of zero which should be differentiated from no data is derived as an analytic result in this manner according to the invention the useful analytic result representing the concentration or activity value of zero can be obtained for such a special sample in known methods such a sample is treated merely as the abnormal one because the signal could not be clearly.