We experienced a patient with membranous nephropathy (MN) and renal cell carcinoma (RCC). Although MN is known to be commonly associated with malignant tumors, association with RCC is rare. In our patient, no malignant focus was found in the major organs examined, except for a small lesion in the right kidney. Diagnosis of a small RCC (1.6 x 1.6 cm), which was made by renal biopsy and histology, was impossible by other, imaging, methods. As surgical treatment for the patient, laparoscopic partial nephrectomy was performed successfully, alleviating the symptoms of nephrotic syndrome for up to 21 months.