A 61-year-old man was admitted to our hospital for examination of the cause of rapid growth of a liver cyst. We found a slight dilatation of bile duct in the vicinity of the liver cyst. Then, we underwent ERCP and found a communication between the bile duct and liver cyst. Bile cytodiagnosis revealed a large quantity of clonorchis eggs. The patient like to do eat raw freshwater fish and we suspected that the acute expansion of the cyst was due to clonorchiasis. Following administration of 40mg/kg praziquantel, the blood clonorchis antibody disappeared and the liver cyst also disappeared after 6 months. We encountered a case of clonorchiasis complicated with growth of a liver cyst. Medical interviews should be conducted carefully along with meticulous examinations.