Hepatic artery pseudoaneurysm(HAP) is a very rare disease but in cases of complication,there is a very high mortality.The most common cause of HAP is iatrogenic trauma such as liver biopsy,transhepatic biliary drainage,cholecystectomy and hepatectomy.HAP may also occur with complications such as infections or inflammation associated with septic emboli.HAP has been reported rarely in patients with acute pancreatitis.As far as we are aware,there is no report of a case caused by acute idiopathic pancreatitis,particularly.We report a case of HAP caused by acute idiopathic pancreatitis which developed in a 61-year-old woman.The woman initially presented with acute pancreatitis due to unknown cause.After conservative management,her symptoms seemed to have improved.But eight days after admission,abdominal pain abruptly became worse again.Abdominal computed tomography(CT) was rechecked and it detected a new HAP that was not seen in a previous abdominal CT.Endoscopic retrograde cholangiopancreatography(ERCP) was performed because of a suspicion of hemobilia as a cause of aggravated abdominal pain.ERCP confirmed hemobilia by observing fresh blood clots at the opening of the ampulla and several filling defects in the distal common bile duct on cholangiogram.Without any particular treatment such as embolization or surgical ligation,HAP thrombosed spontaneously.Three months after discharge,abdominal CT demonstrated that HAP in the left lateral segment had disappeared. Hepatic artery pseudoaneurysm (HAP) is a very rare disease but in cases of complication, there is a very high mortality. The most common cause of HAP is iatrogenic trauma such as liver biopsy, transhepatic biliary drainage, cholecystectomy and hepatectomy. with complications such as infections or inflammation associated with septic emboli. HAP has been reported rarely in patients with acute pancreatitis. As far as we are aware, there is no report of a case caused by acute idiopathic pancreatitis, particularly. We report a case of HAP caused by acute idiopathic pancreatitis which developed in a 61-year-old woman. The woman initially presented with acute pancreatitis due to unknown cause. After conservative management, her symptoms seemed to have improved. But eight days after admission, abdominal pain abruptly became worse again. Abdominal computed tomography (CT) was rechecked and it detected a new HAP that was not seen in a previous abdominal CT. Endoscopic retrograde cholangiopancrea tography (ERCP) was performed because of a suspicion of hemobilia as a cause of aggravated abdominal pain. ERCP confirmed hemobilia by observing fresh blood clots at the opening of the ampulla and several filling defects in the distal common bile duct on cholangiogram. Without any particular treatment such as embolization or surgical ligation, HAP thrombosed spontaneously.Three months after discharge, abdominal CT demonstrated that HAP in the left lateral segment had disappeared.