This paper suggests a electric wheelchair control interface for the improvement of self-respect and free movement of patients, who have ambulatory ability disorder and limited use of upper limbs. The suggested interface method uses an algorithm, which measures muscle activities of both sides’ temporalis and masseter based on NMVC (normalizing to maximal voluntary contraction) and classifies direction pattern by judging the comparative advantage of muscle activities. Tests were done to examine the usefulness of suggested control interface by attaching electrodes to the temporalis and masseter of the test subjects. According to the result of direction pattern classification test, the accuracy was approximately 95%, which is 10% improvement from the accuracy of existing studies. In addition, the time required to reach initial threshold value also decreased by 80%, from 5 minutes to 1 minute.