When a patient with diabetes presents with hepatomegaly and increased level of liver enzymes, glycogenosis or nonalcoholic steatohepatitis (NASH) should be considered. Glycogenosis is mainly developed in patients with type 1 diabetes, when blood glucose level is poorly controlled, when a high dosage of insulin is administered in ketoacidosis, or when glucose is given to control hypoglycemia caused by high dosage of insulin. On the other hand, the main causes of NASH, which are known to mainly affect type 2 diabetes patients, are obesity, dyslipidemia or insulin resistance. Glycogenosis differs from NASH, the former being a reversible change that improves with the control of blood glucose level and the minimum dosage requirement of insulin, and the latter being a progressive disease that may lead to fibrosis or cirrhosis of the liver. However, clinical differentiation of the two diseases is difficult and liver biopsy is helpful for making a definite diagnosis. We present a type 1 diabetes patient with poorly controlled blood glucose level, who have had a frequent history of diabetic ketoacidosis, showing hepatomegaly and a slight increase in liver enzyme level. The patient was diagnosed as diabetic glycogenosis, confirmed by liver biopsy. Strict control of the blood glucose level resulted in rapid improvement showing the reversible nature of the disease.