In this report, we describe our experience treating a rare case of malignant transformation of laryngeal papillomatosis, from which we retained a series of stroboscopic and pathological pictures. None of the known risk factors of irradiation: chemotherapy, smoking, betel nut chewing, or a hereditary tendency toward malignant tumors, were present in this elderly male patient. It is very difficult to elicit the malignant transformation of benign laryngeal papillomatosis in the early stage through the simple observation of stroboscopic features. Aggressive biopsies and careful histological examinations are required to analyze this early, subtle change.