A 51-year-old woman was admitted to our hospital complaining of dyspnea on exertion. Chest high-resolution computed tomography (HRCT) showed diffuse ground-glass opacities with mild traction-bronchiectasis predominantly in the bilateral lower lung fields. On admission, she was suspected of chronic hypersensitivity pneumonitis because she lived in a wet wooden house built 40 years ago. Although her serum KL-6 decreased, her symptoms and X-ray findings worsened during the follow-up period without treatment. We performed a video-associated thoracic surgical lung biopsy. The pathological diagnosis of the biopsy specimens was nonspecific interstitial pneumonia with organizing pneumonia. We suspected her of antisynthetase syndrome, and administered corticosteroids in combination with cyclosporine. After these therapies, her symptoms and HRCT findings improved. An anti-EJ antibody later proved positive. She was diagnosed as having anti-EJ-antibody positive interstitial pneumonia. We should consider the decrease of serum KL-6 during the follow-up period without treatment in interstitial pneumonia with anti-EJ antibody.