In a microcomputer including a processor, a data memory and a controller for controlling the processor and the data memory, the data memory includes a adaptivity degree data group indicative of the adaptivity degree to the fuzzy set, and an area for storing the result of processing. The processor includes an adaptivity degree data pointer, a result store area pointer, a conformity degree data storing register, and a processing number count register. The microcomputer internally includes a fuzzy inference exclusive-instruction, which causes to compare data in the conformity degree data storing register with data designated by the adaptivity degree data pointer, so as to select a smaller one, and compare the selected dam with data designated by the result store area pointer, so as to store a large one at the area for storing the result of processing, designated by the the result store area pointer. The above processings are repealed the number of processing in the processing number count register, while updating the result store area pointer and the adaptivity degree data group pointer.