In a plasma processing method, first processes and second processes are performed alternately. In each first process, a first gas is supplied into a processing vessel from a gas supply system, and a first high frequency power is supplied from a first high frequency power supply. In each second process, the first high frequency power is supplied from the first high frequency power supply continuously from a first process which is performed just before the corresponding second process. In each second process, a gas switching signal for switching the gas from the first gas to the second gas is applied to the gas supply system. Further, a supply of a second high frequency power is begun by a second high frequency power supply when a parameter such as a load impedance exceeds a threshold value after the gas switching signal is applied to the gas supply system.