We present herein the case of a 45-year-old man with a coronary artery aneurysm (diameter 19 mm) in the proximal part of the left anterior descending branch associated with eosinophilic granulomatosis with polyangiitis (EGPA). As coronary angiography showed #6 : 100% and #12-2 : 90%, and Tc-99 m myocardial scintigraphy showed exertional ischemia in the anterior septum, revascularization was considered to be indicated. Prednisolone and mepolizumab were administered preoperatively to suppress the activity of vasculitis due to eosinophilia, and surgery was performed when the eosinophil count normalized. The patient underwent off-pump coronary artery bypass grafting (LITA-LAD, SVG-OM2). The patient was discharged, and the postoperative course was uneventful. In coronary artery bypass grafting for EGPA, eosinophils may infiltrate the internal thoracic artery and result in vasculitis, which may affect the patency rate. Perioperative management of vasculitis may thus be important.