In order to improve the quality of life of persons who lost their limb due to an accident or a sickness, many myoelectric artificial arms have been proposed. To control the motion of the elbow joint of the myoelectric arm, the EMG signals of the biceps brachii and the triceps brachii muscles are frequently used as input signals. However, since both muscles are the biarticular muscles between the shoulder joint and elbow joint, the amount of the EMG signals of these muscles are affected by the motion of the shoulder joint. In this paper, a control method for a myoelectric arm is proposed in order to cancel the influence of the shoulder joint motion on EMG signals is removed by using the neuro-fuzzy modifier in order to realize proper elbow motion. The effectiveness of the proposed method has been evaluated by performing experiments.