A cleaning process optimization device includes a machine learning device that learns a cleaning condition when cleaning an object to be cleaned. The machine learning device includes: a state observation unit that observes cleaning condition data indicating the cleaning condition, and contamination state data indicating a contamination state of the object to be cleaned measured before cleaning as a state variable representing a current state of environment; a determination data acquisition unit that acquires determination data indicating an adequacy determination result on accuracy of a contamination state of the object to be cleaned after cleaning; and a learning unit that learns the cleaning condition when cleaning the object to be cleaned in association with the contamination state data using the state variable and the determination data.