A 68-years-old and 148 cm tall female with lung cancer was operated on a left lower lobectomy via posterolateral thoracotomy. A 35 Fr double-lumen endobronchial tube was smoothly inserted and the tip was placed in the left main bronchus whose position was confirmed by fiberoptic bronchoscope. After lobectomy and lymph node dissection were completed, 1-lung ventilation was terminated, the left chest cavity was filled with saline, and an air-leak test was performed. Immediately after the initiation of bilateral lung ventilation, massive air-leak was observed in the left hilar region and the saline in the chest regurgitated into the airway, and she fell into critical ventilatory insufficiency. After sucking the saline in the chest, thorough observation revealed a 3 cm-long rupture of the membranous portion of the left main bronchus. The rupture was manually occluded and ventilatory insufficiency was avoided, then the tip of the endobronchial tube was re-inserted into the right main bronchus and right single lung ventilation was initiated. The rupture was closed by a 4-0 polydioxanone (PDS) running suture with no coverage. The patient was extubated immediately after the operation. Ten days later, she had a tiny bronchial fistula, and it was cured by chest drainage only, and she discharged home on the 48th postoperative day.