Although the operative results have been improving since the air drill was introduced for cervical laminectomy instead of an ordinary rongeur, post-laminectomy complications, such as postoperative fragility of the cervical spine to acute neck trauma, posterior spur formation at the vertebral body, and malalignment of the lateral curvature have still remained as unsolved problems. In order to avoid these disadvantages, a new surgical technique called “expansive open-door laminoplasty” was devised by the author in 1977, which is relatively easier, safer, and better than the ordinary laminectomy from the standpoint of structural mechanics of the cervical spine. The operative procedure is described in detail. Operative results in the patients with cervical OPLL, spondylosis, and canal stenosis were satisfactory, and optimal widening of the AP diameter of the spinal canal is considered to be over 4 mm. From this procedure a bilateral, open-door laminoplasty has been devised for extensive exploration at the intradural space.