A 69-year-old woman complaining of a cough was admitted to our hospital. Chest X-ray showed a mass in the right lower lung field. Chest computed tomography (CT) showed a tumor with notch, 3 cm in diameter, in the right lower lobe (S9-S10). The tumor was diagnosed as adenocarcinoma by the biopsy under chest CT. The patient underwent right lower lobectomy (ND2a). The tumor was whitish solid mass, 35 x 34 x 29 mm in size. Histopathologically, the tumor was diagnosed as clear cell adenocarcinoma with a component of well-differentiated fetal adenocarcinoma (WDFA), pT2N0M0, stage IB. The patient was discharged and received postoperative chemotherapy (UFT). The patient has been doing well without any tumor recurrence for 1 year postoperatively.