A 77-year-old man with chronic kidney disease was presented to our hospital because he developed involuntary movement of bilateral upper limbs and dysarthria during dialysis. On admission, he showed myoclonus on bilateral upper limbs and dysarthria caused by involuntary movement of the tongue. We diagnosed metabolic involuntary movements due to renal failure. Myoclonus on bilateral upper limbs disappeared on the next day, however, involuntary movement of the tongue remained. Transoral motion-mode ultrasonography (TOMU) revealed that the tongue moved with a frequency of 4–5Hz intermittently, and we made diagnosis of lingual myoclonus. TOMU can measure the frequency of involuntary movements of tongue. TOMU is useful for the diagnosis of oral involuntary movement.