We report a case of IgG4-related periaortitis of the descending aorta manifested as a contained rupture of penetrating atherosclerotic ulcer(PAU). A 67-year-old male was admitted to our hospital complaining about chest pain. Computed tomography(CT) and magnetic resonance imaging revealed PAU with extravasation of the descending aorta and thickening of surrounding tissues. Fluorodeoxyglucose-positron emission tomography (FDG-PET) CT demonstrated abnormal accumulation of FDG at the thickening sites, and serum IgG4 value was abnormally high. The descending aorta replacement was performed and intraoperative findings showed a marked thickening of the mediastinal tissue around the descending aorta and the ulceration of the intima penetrating to the mediastinum. In histopathological examination, the adventitial thickening due to marked fibrosis and the ulceration of the intima accompanying infiltration of IgG4 positive plasma cells were observed. IgG4-related thoracic periaortitis can invade not only to the adventitia but to the intima, and can cause PAU. For aortic diseases with thickening of periaotic tissues, it is necessary to keep in mind the possibility of IgG4-related aortic disease, and serum IgG4 values are useful for diagnosis.