The frequency of a visceral mycosis grows definitely higher with an immunocompromised host. Invasive fungal infection can be controlled by means of development of early diagnosis and antifungal therapy. In these types of cases, it is difficult to establish an antemortem diagnosis of invasive pulmonary aspergillosis and most of them were diagnosed postmortem. A patient was diagnosed as aspergillosis from the clinical and serological features. This patient underwent successful therapy during remission induction therapy of acute myelocytic leukemia (AML). A 26-year-old male was admitted to our hospital because of leukocytosis with a diagnosis of AML made by reviewing peripheral blood smears and bone marrow aspirate. After remission induction therapy, he was still febrile in spite of treatment with a broad spectrum antibiotics and empiric therapy of fluconazole. Unfortunately shadowing appeared on the chest radiograph and aspergillus antigen was detected from the serum and the sputum. Consequently, the patient who suffered from invasive pulmonary aspergillosis was diagnosed and treated with intravenous amphotericin B and flucytosine. The radiological shadow improved but AML relapsed, therefore, remission induction therapy of AML was started again but he died of sepsis caused MRSA. In the postmortem histopathological examination the lung tissues, the hyphae could not be confirmed while, in immunohistochemical examinations of the lesion at the left S8, aspergillus antigens were detected around the small necrotic lesions and in the polymorphologic giant cells. We emphasize that invasive pulmonary aspergillosis is very difficult to diagnose whereas active examinations and clinical early diagnosis may lead to more effective therapy and the prognosis.