Steroid sulfatase (STS) deficiency is one of the causes of ichthyoses. STS genes on the X chromosome is responsible for this disease. Therefore, STS deficiency is also called X-linked ichthyosis. Herein we report a case of STS deficiency complicated by bilateral undescended testis. A5-year-old-boy with STS deficiency was referred to our hospital because of bilateral undescended testis. We performed bilateral orchiopexy.