The patient was a 70-year-old woman. She was admitted to our hospital complaining of fever and dyspnea. Chest CT scan showed a 50×30-mm tumorous shadow in S6 of the left lung and honeycomb lung in both lower lobes. As the result of cytodiagnosis with ultrasonic echo, adenocarcinoma was diagnosed. Clinical stage was IIIA (T3N2M0). We selected carboplatin and paclitaxel with bevacizumab as first-line chemotherapy, but at 7 days after the initiating it, the chest X-ray showed left pneumothorax. A chest drainage tube was placed in the left thoracic cavity. The patient was treated repeatedly pleurodesis with minocycline and OK-432. The pneumothorax required 3 weeks to cure. We selected carboplatin and paclitaxel without bevacizumab for the second course, and the pneumothorax did not recur. Pneumothorax was a serious adverse event associated with bevacizumab-containing chemotherapy. It is necessary to be aware of the possibility of pneumothorax when we treat lung adenocarcinoma with bevacizumab-containing chemotherapy.