The patient was a 57-year-old man who was diagnosed with multiple lung metastases of sigmoid colon cancer. The patient developed progressive disease after 8 courses of bevacizumab + capecitabine and oxaliplatin therapy, therefore, bevacizumab + irinotecan, leucovorin, and 5-fluorouracil therapy was started. During the fifth course, he experienced pain on the left side of his chest. On computed tomography, bleeding from the pulmonary metastatic lesions was suspected. Two days later, a pneumothorax was detected. Although several cases of pneumothorax induced by bevacizumab have been reported, this case is the first documentation that bevacizumab caused a rupture of the lung metastatic lesion, leading to a pneumothorax.