We report a case of HER2-positive metastatic breast cancer achieved a complete response(CR)to paclitaxel(PTX) and trastuzumab(HER) in combination with pertuzumab(PER) in 5th therapy. A 69-year-old woman was diagnosed left breast cancer and underwent mastectomy and sentinel lymph node biopsy in January 2011. Pathological examination revealed an invasive ductal carcinoma that was ER 0%, PgR 0%, HER2(3+), Ki-67 67% and node negative. Two years after the operation, she found multiple lung metastases in both lungs. She was administered drug treatment as HER2-positive metastatic breast cancer, but multiple lung metastases got worse after 4th treatment. Weekly PTX, trastuzumab and pertuzumab were administered as 5th therapy. After 2 months, lung metastases diminished significantly. After 44 courses of drug treatment, positron emission tomography computed tomography(PET-CT)scan revealed CR. She wanted to cease treatment, so she continues to get CT scan every half a year and the CR has been maintained.