There is provided a technique of cleaning an inside of a process container, including: (a) removing substances adhered in a process container set at a first temperature by supplying a first gas at a first flow rate into the process container and exhausting the inside of the process container; (b) physically desorbing and removing residual fluorine in the process container set at a second temperature by supplying a second gas at a second flow rate into the process container and exhausting the inside of the process container; and (c) chemically desorbing and removing residual fluorine in the process container set at a third temperature by supplying a third gas at a third flow rate into the process container and exhausting the inside of the process container.