We report a case of milk of calcium renal stone within a calyceal diverticulum in the patient with left ureteral tumor. The patient was a 77-year-old-man with the chief complaint of asymptomatic microscopic hematuria. A plain film revealed round opaque calcific densities in the left kidney in the supine position and a dense crescent-shaped shadow with a horizontal border in the upright position. An intravenous pyelography showed left hydronephrosis and calculi within a calyceal diverticulum. Computed tomography in the supine position revealed layering of the calcifications in cystic lesion of the left kidney accompanied by left hydronephrosis due to a soft mass in the left ureter and a right renal cyst. Retrograde pyelography revealed a filling defect of the middle portion of the left ureter. Under the diagnosis of milk of calcium renal stone and left ureteral tumor, left total nephroureterectomy and partial cystectomy was performed. Pathological findings indicated transitional epithelium of the diverticulum wall and grade 1 transitional cell carcinoma of the left ureteral tumor.