We report a case of chronic type B aortic dissection in a 70-year-old man. At an outpatient hospital, he was found to have an expanded dissecting descending aortic aneurysm and was transferred to our hospital for thoracic endovascular aortic repair (TEVAR). A stent graft was successfully placed in the proximal descending thoracic aorta (DTA) to close the primary entry. Postoperative computed tomography (CT) revealed persistent contrast enhancement of the false lumen in the DTA that was suggestive of an endoleak. However, the origin and flow direction of the endoleak were uncertain, and classification of the endoleak was difficult. Hence, the echocardiographic paravertebral approach (PVA) was performed. Both the true lumen and false lumen were clearly visualized and retrograde flow from the intercostal artery into the false lumen was demonstrated by color Doppler examination. These findings suggested that the endoleak originated from the intercostal artery (type II) rather than the proximal end of the stent graft (type Ia). Hence, it was concluded that the patient should be observed conservatively. Follow-up CT at 8 months post-TEVAR showed no expansion of the maximal diameter of the DTA. In this case, the utility of PVA for detection and classification of an endoleak after TEVAR was confirmed.