Cutting conditions have an effect on machining efficiency, machining cost and machining time. Thus, a multitude of methods have been proposed to determine the optimum cutting conditions. But each in itself is specific and has limited applicability to the situation for which it was devised. Hence, it may be said that the cutting conditions which are led from those methods are only subconditions in the machining scene. On the other hand, the skilled machinist can continuously adjust operations in terms of machining efficiency, machinability and cost. This adjustment is done by means of cutting conditions. In this paper, the system is proposed to simulate the machinist's thinking process which set the appropriate cutting conditions based on evaluation of cutting state. The thinking process is constructed by fuzzy integral and hill-climbing. The accuracy of the system's output was examined by the experiments under various cutting conditions in turning, and the validity of the system was confirmed.