Disclosed is a plasma processing method which includes a gas supplying process, a power supplying process, and an etching process. In the gas supplying process, a processing gas is supplied into a processing container in which an object to be processed is disposed. In the power supplying process, a plasma generating power of a frequency ranging from about 100 MHz to about 150 MHz as a power for generating plasma of the processing gas supplied into the processing container, and a biasing power which is a power having a frequency lower than that of the plasma generating power are supplied. In the etching process, the object to be processed is etched by the plasma of the processing gas while the biasing power is pulse-modulated so that the duty ratio ranges from about 10% to about 70% and the frequency ranges from about 5 kHz to about 20 kHz.