A 45-year-old man was referred to our department for further examination of the renal complicated cyst which was found incidentally by ultrasonography. Another complicated cyst in the left kidney was detected by subsequent dynamic CT and ultrasonography, which suggested bilateral cystic renal cell carcinoma. Bilateral partial nephrectomy was performed. Intraoperative ultrasonography was useful for diagnosis of multilocular cystic renal cell carcinoma (MCRCC). It disclosed multiple septa of the right renal complicated cyst which were not revealed by any preoperative examinations. It was also a useful adjunct to partial nephrectomy. It helped to identify the extent of deep intra-parenchymal lesions. The final diagnosis was bilateral synchronous multilocular cystic renal cell carcinoma. This is the second case of bilateral synchronous multilocular cystic renal cell carcinoma reported in Japan. We reviewed the clinical characteristics of 59 cases of MCRCC in the Japanese literature including the present case.