Diffuse pulmonary ossification is rare disease of unknown etiology. Since the first description by Luschka in 1856, about 140 cases have been reported worldwide, but no such case has been reported in Korea yet. We report 40-year-old woman who was diagnosed as diffuse nodular pulmonary ossification on open lung biopsy. She has no respiratory symptoms & physical findings and no previous disease history. She was incidentally found to have multiple pulmonary nodules on roentgenographic examination. Open lung biopsy was done for above lesion and She was proven to have diffuse nodular pulmonary ossification. She was followed by roentgenographic examination and showed no progression.