Alveolar adenoma (AA) is a rare lung benign tumor originated from type II pneumocytes. It presents as a well-defined nodule in clinical images, but is difficult to differentiate from early-stage lung cancer. We treated a 58-year-old woman with a small-sized AA measuring 8 x 6 mm in the upper lobe of the left lung by performing a thoracoscopic resection. The AA does not cause any symptoms and it is often incidentally detected as an abnormal shadow. There have been no reported cases of recurrence after a resection of AA, but a subsequent increase in such cases is expected, and we believe that it is necessary to understand the characteristics of this typical benign lung tumor.