CLEANING ENDPOINT DETECTION METHOD

PROBLEM TO BE SOLVED: To provide a cleaning endpoint detection method capable of suppressing damage on a member constituting a deposition device, by enhancing accuracy of cleaning endpoint detection by a simple method.SOLUTION: A cleaning endpoint detection method includes a step for starting supply of cleaning gas, i.e., fluorine-based gas, into an evacuated chamber 11, and continuously measuring the pressure of exhaust gas discharged from the chamber 11 while cleaning, a step for continuously measuring the absorbancy of fluorine gas contained in the fluorine-based gas obtained by irradiating the exhaust gas of atmospheric pressure with light, a step for continuously acquiring the concentration of fluorine gas contained in the exhaust gas on the basis of the absorbancy of fluorine gas, an endpoint detection step for detecting the endpoint of cleaning on the basis of the pressure of exhaust gas and concentration of fluorine gas, and a step for stopping supply of the fluorine-based gas after detecting the endpoint of cleaning.