of width of each fuzzy model the reliability of the obtained fuzzy model can be expressed by the width of the fuzzy values of the obtained fuzzy model since the final result is obtained from the fitting degrees of the two fuzzy models the combined fuzzy model is obtained within the one of the two fuzzy models that has a high reliability thus the combined fuzzy model will have a high reliability as has been described above according to the fuzzy data processing device of the present invention the two fuzzy regression models under two different conditions are used to obtain one fuzzy regression model such that the maximum output of the fitting degree of the regression output from both fuzzy regression models is obtained thus the preciseness of the estimation can be improved while considering the reliability of the two models referring to fig7 an abnormal fuzzy data detecting device according to the present invention is shown when compared with the fuzzy data processing device shown in fig4 the abnormal fuzzy data detecting device of fig7 has a fitting degree comparator 9 instead of fitting degree maximum detector 8 by the input data x 0 and z 0 estimated values yx and yz are obtained at fuzzy regression model memories 5 and 6 respectively then in the fitting degree calculator 7 the select minimum calculation is carried out so as to produce a signal representing a lower level of the two levels yx and yz for every y in the fitting degree comparator 9 the peak point of the shaded portion is compared with a predetermined level when the compared result is such that the peak point is less than the predetermined level.