A 72-year-old man was admitted to our hospital due to abnormal shadow in the right hilum by a routine chest X-ray. When we had another look at a chest X-ray that had been taken 6 years before, we had found a pulmonary nodule of 18 mm in size. The chest X-ray and computed tomography (CT) taken at admission showed a round nodule with calcification in the same site, with increasing in size to 30 mm. The tumor could not be clinically diagnosed and the surgery was scheduled because the nodule had grown and the possibility of a malignant tumor was suggested. At surgery, the tumor was easily enucleated and the pathological diagnosis was chondromatous hamartoma. Although pulmonary hamartoma is a benign tumor, operation should be performed when the tumor had grown.