1. An apparatus for setting membership functions, which comprises: a setting means for setting membership functions and corresponding identification codes for input and output variables, each of said membership functions having a predefined shape; means for checking whether there is identity in shape among membership functions set for each input and output variable and for each identification code; means for assigning different identification numbers to set membership functions which are different in shape from one another and identical identification numbers to set membership functions processing an identity in shape; a first memory device for storing data, which represents a set membership function, in corresponding with the identification number assigned thereto; and a second memory device for storing in a correlated manner names of the input or output variables, the identification numbers assigned to the differently shaped membership functions associated with respective input or output variables, and the identification codes of the membership functions which correspond to the identification numbers.