A 70-year-old woman was admitted to our hospital because of rapidly progressive cerebellar ataxia. Neurological examinations showed saccadic eye movement, downbeat nystagmus, scanning speech, proximal dominant muscle weakness and severe truncal and limb ataxia. Based on these clinical features, she was suspected to have paraneoplastic cerebellar degeneration (PCD), although the malignant tumor was not detected through clinical intensive surveys. Her serum and CSF revealed to have anti-Purkinje cell antibodies immunohistochemically, and western blot analysis showed that they reacted with 58 kd band. In view of previous reports of PCD, she was strongly suspected to have gynecological cancers. The trial laparotomy found early stage fallopian tubal cancer, which had not been detected by CT scan, ultrasonogram and MRI. It is important to detect and characterize these autoantibodies found in the PCD patients for early diagnosis and treatment of underlying cancer.