Extended thymectomy in conjunction with a collar incision of the neck was performed thoracoscopically for a 64-year-old women with myasthenia gravis. Although this patient had Osserman type II B myasthenia gravis not associated with a thymoma, the clinical symptoms were alleviated after the surgery. Although this surgical procedure has the disadvantage such as of being time-consuming, it also has various advantages such as: 1) extended thymectomy can be performed without a midsternotomy, 2) the wound is small and not prominent, 3) surgical invasiveness is slight, and 4) postoperative pain is mild. This method was considered to be an extremely useful surgical method which should be used in future for cases of myastenia gravis not associated with a thymoma.