A 45-year-old man was diagnosed with bacterial pneumonia and prescribed garenoxacin by a local doctor. However, his pneumonia worsened and he visited our department. After administration of a combination drug (tazobactam/piperacillin), his pneumonia improved and he was discharged on the 9th day of hospitalization, but the next day he was re-hospitalized due to fever and respiratory distress. Because we heard that the patient had disinfected a room in his house by spraying sodium hypochlorite in order to prevent coronavirus disease 2019 (COVID-19), we suspected acute lung injury caused by inhalation of the drug. On re-hospitalization, being away from his home improved the symptoms without administration of antibacterial drugs. After that, an exposure test was conducted and the symptoms recurred in approximately four hours. Thus, we diagnosed his illness as highly suspicious acute lung injury caused by sodium hypochlorite disinfectant. During the COVID-19 epidemic, it is particularly important to realize the possibility of acute lung injury caused by the spraying of disinfectant.