A case of Grawitz's tumor metastasizing to the cauda equina is presented. A 51-year-old male was hospitalized due to severe low back pain radiating to the left lower extremity. Neurological examination showed only hyporeflexia of the left patella reflex and positive Lasegue's sign. MRI showed intradural mass at the L4 level. Preoperatively, we diagnosed a cauda equina tumor. A laminectomy of both L3 and L4 was performed, and total removal of the cauda equina tumor was performed. Microscopically, the tumor cells were large, the appearance of the cytoplasm ranging from optically clear with sharply outlined boundaries, to deeply granular, with many transitional forms. These histological findings were typical findings of Grawitz's tumor, and were the same as those of this patient's renal tumor. Finally, we diagnosed Grawitz's tumor metastasizing to the cauda equina. Metastatic cauda equina tumor from outside the central nervous system is very rare and only 7 cases have been reported. This case is the first one of Grawitz's tumor spreading to the cauda equina.