Trigeminal motor neuropathy is a rare disorder which involves only motor fiber in trigeminal nerve. We experienced a 58-year-old man with muscle weakness and wasting of left masticatory muscles for 3 weeks. He had suffered from the same event on the right side 13 years ago. He had no sensory dysfunction and Brain CT revealed no gross abnormality. All the laboratory findings were negative and the EMG revealed chronic denervating process in bilateral masseter and temporalis muscles. He has improved after steroid therapy.