In a plasma processing method in which multiple cycles, each of which includes a first stage of generating plasma of a first processing gas containing a first gas and a second stage of generating plasma of a second processing gas containing the first gas and a second gas, are performed, a time difference between a start time point of a time period during which the second stage is performed and a start time point of an output of the second gas from a gas supply system is decided automatically according to a recipe. A delay time corresponding to flow rates of the first gas and the second gas in the second stage is specified from a function or a table. The output of the second gas is begun prior to the start time point of the second stage by a time difference set based on the delay time.