Etching method

An etching method of etching a periodic pattern formed by self-assembling a first polymer and a second polymer of a block copolymer that is capable of being self-assembled includes introducing a gas into a processing chamber; setting a frequency of a high frequency power supply such that a great amount of ion energy is distributed within a range smaller than ion energy for generating an etching yield of the first polymer and equal to or larger than ion energy for generating an etching yield of the second polymer, and supplying the high frequency power into the processing chamber from the high frequency power supply; generating plasma from the gas introduced in the processing chamber by applying the high frequency power; and etching the periodic pattern on a processing target object mounted on a susceptor 16 by using the generated plasma.