A 21-year-old woman reported continuous moderately severe headache in the right frontotemporal region, accompanied by exacerbations with cranial autonomic symptoms and restlessness. The exacerbations appeared several times a week over one to several hours. The patient was diagnosed with hemicrania continua (HC) according to the 3rd edition of the International Classification of Headache Disorders. Because production of the oral indomethacin was discontinued in April 2020, acemetacin, a prodrug of indomethacin, was administered (90 mg/day) and gradually increased to 180 mg/day over 2 months. No recurrence of HC developed. No reports of HC treated with acemetacin have been previously reported in Japan. We suggest that randomized control trials should be performed.