Since fiscal year 2015, our hospital has conducted regular hospital inspections by a medical engineer (ME). About 1 year after the start of this inspection, fungi and common bacteria were detected, so we searched for the cause and report here successful cleanup of the incubator. When the incubator was cleaned during a periodic inspection, the ME discovered that dirt mainly adhered to the fan and the bed rest. Also, fungi were detected from the fans, so the ME cleaned and disinfected all the fans and then switched to a process of washing the central supply room. Following this process, bacteria were no longer detected from inside the incubator, but they have been consistently detected from the fans. We have no reported cases of patient infection, and we believe this is because the ME is responsible for periodic cleaning against bacteria and for conducting inspections. This demonstrates that successful cleaning of the incubator led to control of the spread of infectious diseases.