We treated a 32-year-old man with hearing loss in the right ear followed by severe muscle weakness of the extremities. When admitted to hospital by ambulance, the serum potassium level was 1.5mEq/L. The muscle weakness was improved following administration of potassium chloride but the hearing impairment continued. Hearing level of the right ear was extremely impaired at the level of 60-105dB, while hearing in the left ear was fairly normal. Spontaneous nystagmus was also present. The triiodothyronine level was 290ng/dl, thyroxine 14.4 μg/dl, thyroid stimulating hormone (TSH) 0.84 μU/ml, and the anti-TSH-receptor antibody was positive. Attaining an enthyroid state, the patient was discharged on 80th hospital day with the continuous medication of Methimazole. This is a very rare case of sudden deafness complicated by hypokalemic paralytic attacks. Circulatory insufficiency and electrolytes imbalance in the right inner ear was assumed to have caused the deafness.