An automatic analyzer comprising: a sample vessel for containing a sample to be measured; a reagent vessel for containing a reagent to be reacted with the sample; a reaction vessel in which to mix the sample and the reagent; a sample dispenser for dispensing the sample from the sample vessel into the reaction vessel; a reagent dispenser for dispensing the reagent from the reagent vessel into the reaction vessel; a stirrer for stirring the sample and the reagent contained in the reaction vessel to obtain a mixed solution; a measurement section for obtaining a plurality of measurement data points during the progress of reaction of the mixed solution; a storage section for storing one or more approximation formula to generate an approximation curve from the measurement data points; and a data processing section having a calculation section for generating an approximation curve from the measurement data points and an abnormality judgment section for performing abnormality judgment; characterized in that the calculation section is adapted to select at least one approximation formula, to generate the approximation curve based on the selected approximation formula and to calculate a shape descriptor from the generated approximation curve, and the abnormality judgment section is adapted to perform abnormality judgment based on the shape descriptor; the data processing section is adapted to generate as the shape descriptor at least either one of shape descriptors T, D, Q, and P, where, provided that a tangent to the approximation curve right after the start of reaction is a first line and that a line approaching the approximation curve is a second line, the shape descriptor T is the time at which the first line and the second line intersect, the shape descriptor D is the difference between the first line and the second line at the start of the reaction, the shape descriptor Q is the value of the first line at the start of the reaction, and the shape descriptor P is the slope of the second line. a sample vessel for containing a sample to be measured; a reagent vessel for containing a reagent to be reacted with the sample; a reaction vessel in which to mix the sample and the reagent; a sample dispenser for dispensing the sample from the sample vessel into the reaction vessel; a reagent dispenser for dispensing the reagent from the reagent vessel into the reaction vessel; a stirrer for stirring the sample and the reagent contained in the reaction vessel to obtain a mixed solution; a measurement section for obtaining a plurality of measurement data points during the progress of reaction of the mixed solution; a storage section for storing one or more approximation formula to generate an approximation curve from the measurement data points; and a data processing section having a calculation section for generating an approximation curve from the measurement data points and an abnormality judgment section for performing abnormality judgment; characterized in that the calculation section is adapted to select at least one approximation formula, to generate the approximation curve based on the selected approximation formula and to calculate a shape descriptor from the generated approximation curve, and the abnormality judgment section is adapted to perform abnormality judgment based on the shape descriptor; the data processing section is adapted to generate as the shape descriptor at least either one of shape descriptors T, D, Q, and P, where, provided that a tangent to the approximation curve right after the start of reaction is a first line and that a line approaching the approximation curve is a second line, the shape descriptor T is the time at which the first line and the second line intersect, the shape descriptor D is the difference between the first line and the second line at the start of the reaction, the shape descriptor Q is the value of the first line at the start of the reaction, and the shape descriptor P is the slope of the second line.