Chemical pneumonitis is caused by the inhalation of noxious chemical substances and is a cause of occupational lung disease. Nitric acid, which is a one of the common air pollutants and a potential oxidant for refining and cleansing of metals, has a chance for occupational and environmental exposure. A 52-year-old man visited our hospital due to coughing and dyspnea after the inhalation of nitric acid fumes at his workplace. He had conditions of tachypnea (respiratory rate 26 /min) and hypoxemia (PaO² 42.6 mmHg, SaO² 80.2% in room air) in our emergency department. The chest radiographs showed diffuse interstitial infiltrates and ground glass opacity in both lungs. The patient made improvements in clinical symptoms and chest radiography after being given a supply of oxygen, antibiotics, and bronchodilator therapy without systemic glucocorticoid therapy. On his follow up visit after 4 weeks, he showed no symptoms and sequelae, and the pulmonary function test showed a normal pulmonary function.