1. An apparatus for automatically generating fuzzy reasoning rules, comprising a controller, said controller comprising: rule memory for storing rule parameters of membership functions constituting fuzzy reasoning rules representing relationships between input data and output data, each of said fuzzy reasoning rules being composed of antecedents and consequents; fuzzy reasoning means, connected to said rule memory, for performing a fuzzy reasoning process based on said rule parameters of membership functions constituting said fuzzy reasoning rules stored in said rule memory and outputting results of said fuzzy reasoning process; reasoning error calculation means, connected to said fuzzy reasoning means, for calculating a reasoning error and a change in the reasoning error to obtain a calculated reasoning error and a calculated change based on the results of said fuzzy reasoning process outputted from said fuzzy reasoning means and said plurality of pairs of predetermined input and output data; parameter tuning means, connected to said rule memory, said fuzzy reasoning means and said reasoning error calculation means, for adjusting said rule parameters of membership functions constituting said fuzzy reasoning rules stored in said rule memory, based on the results of said fuzzy reasoning process outputted from said fuzzy reasoning means and a plurality of pairs of predetermined input and output data for said fuzzy reasoning process which are previously determined by a rule designer, said parameter tuning means being enabled to operate when said change in the reasoning error calculated by said reasoning error calculation means is larger than a predetermined second threshold value; and rule generation means, connected to said rule memory and said reasoning error calculation means, for newly generating rule parameters of membership functions constituting said fuzzy reasoning rules and storing said newly generated rule parameters of membership functions constituting the fuzzy reasoning rules in said rule memory, said rule generation means being enabled to operate when said change in the reasoning error calculated by said reasoning error calculation means is equal to or smaller than said predetermined second threshold value, wherein said reasoning error calculation means alternately enables said parameter tuning means and said rule generation means repeatedly to operate until said reasoning error calculated by said reasoning error calculation means is equal to or smaller than a predetermined first threshold value.