This is a case of a boy with autosomal dominant cerebellar ataxia (SCA type 2), which was confirmed by DNA analysis. A 9-year-old boy had been suffering from tremor in both arm and leg for 5 years. After traffic accident, a year ago, the symtoms were more aggravated, and he visted our hospital. The boy showed slow saccades, decreased DTR, ataxic gait and limb ataxia. We analyzed DNA repetition, which revealed positive for the SCA2 expanded repeat.