A processing apparatus includes a plurality of first gas supply channels configured to supply a plurality of gases to the process chamber, a second gas supply channel configured to supply a gas to the process chamber, the gas being used in processing the target substrate, a plurality of first valves configured to open and close the plurality of first gas supply channels, a second valve configured to open and close the second gas supply channel, and a controller. One of the plurality of first valves is a follow-up target valve. The controller controls opening/closing operation of the plurality of first valves such that opening durations of the plurality of first valves do not overlap with each other, and controls opening/closing operation of the second valve such that opening duration of the second valve has a predetermined time relationship with opening duration of the follow-up target valve.