Time-course data that has been obtained by measuring, in time series, a change in the density of a sample material by a color reaction thereof is input. A regression curve generation unit generates a regression curve that approximates the time-course data. A standard deviation obtainment unit obtains the value of a standard deviation representing the distribution of the approximation error of the regression curve with respect to the time-course data. A standard deviation comparison judgment unit compares the value of the standard deviation and a predetermined threshold value that is stored in a standard deviation storage unit with each other. When the value of the standard deviation is greater than the threshold value, the standard deviation comparison judgment unit judges that a position shift of the sample material with respect to a sample table is present and outputs the result of the judgment.