A processing method includes a first process of exposing a first sensor to a processing space within a chamber and blocking a second sensor from the processing space within the chamber; a second process of supplying a first processing gas containing a precursor gas into the chamber; a third process of controlling a state within the chamber based on a measurement value of the first sensor; a fourth process of blocking the first sensor from the processing space within the chamber and exposing the second sensor to the processing space within the chamber; a fifth process of supplying a second processing gas containing a reactant gas into the chamber; and a sixth process of controlling the state within the chamber based on a measurement value of the second sensor. The first process to the six process are repeatedly performed multiple times.