The patient was a 32-year-old man with a previous history of bronchial asthma. He was admitted with chief complaints of dyspnea and skin rash associated with itching of the palms and soles of the feet, which began 2 weeks earlier. Because of the presence of cardiac failure and increase in the peripheral blood eosinophil count, eosinophilic myocarditis (EM) was suspected. His blood pressure gradually decreased and the patient went into cardiogenic shock. Therefore, endomyocardial biopsy was performed and was immediately followed by corticosteroid therapy and intra-aortic balloon pump (IABP) placement. With the findings of eosinophil infiltration associated with myocardial interstitial edema on endomyocardial biopsy, EM was diagnosed. In this case, early therapeutic intervention led to resolution of shock resolved and improvement of the peripheral blood eosinophilia and cardiac function; the patient was discharged 33 days after the onset of symptoms. EM is a rare cardiomyopathy in which myocardial eosinophil infiltration is seen. Although it has been perceived as having a mild clinical course, this report described a severe case of EM associated with cardiogenic shock, which improved as a result of early diagnosis and therapeutic intervention.