Alveolar adenoma is a rare pulmonary neoplasm. This report describes a case of alveolar adenoma of the lung in a 61-year-old woman. A chest X-ray demonstrated a solitary round pulmonary nodule. After six years of observation, this lesion had increased in size. Thoracoscopic left upper segmentectomy was performed on account of a possible low-grade malignant tumor. Histologically, the neoplastic epithelial cells, which had the appearance of proliferative type II pneumocytes, revealed no evidence of malignancy. These findings indicated that the tumor is alveolar adenoma of the lung. The course of disease remains uneventful, one year after the resection.