The patient was a 45-year-old man, with no complaints. It was pointed out that he had a cystic lesion in the liver by abdominal ultrasonography at routine medical check-up. With close examinations, the tumor was multilocular cystic lesion in the right lobe of the liver, whose size was 35mm in diameter. We supposed it was a biliary cystadenoma (adenocarcinoma), echinococcosis, or degenerated hemangioma. And we performed partial hepatectomy. Finally, it was diagnosed as pure type monolobar Caroli's disease by pathological examination. This was a rare case of Caroli's disease which arose limitedly in monolobe. And we could curatively resect it by hepatectomy.