A 53-year-old man was diagnosed with polymyositis (PM) in 1997 and treated with prednisolone. The subjective symptoms of pneumonitis were poor. However, the KL-6 values were elevated to 2230 IU/l in March 2001. Abdominal computer tomography findings revealed a pancreatic-tail tumor and multiple liver nodules, diagnosed as primary pancreatic adenocarcinoma with multiple liver metastasis. The stage of the pancreatic cancer was IV, and curative surgery of the tumor was not indicated. Chemotherapy and radiotherapy were administered for the liver metastasis. However, these therapies were ineffective against the tumors. The patient died on 12 September 2001. If a high level of KL-6 is found without the increasing activity of lung disease containing interstitial pneumonia in PM patients, examination for the internal malignancies including pancreatic cancer should be performed, although cases of PM with a significantly high level of KL-6 associated with pancreatic cancer are rare.