A plasma etching method is provided for forming a hole using a first processing gas to etch a silicon layer of a substrate to be processed including a silicon oxide film that is formed into a predetermined pattern. The method includes a first depositing step (S11) of depositing a protective film on a surface of the silicon oxide film using a second processing gas containing carbon monoxide gas, a first etching step (S12) of etching the silicon layer using the first processing gas, a second depositing step (S13) of depositing the protective film on a side wall of a hole etched by the first etching step using the second processing gas, and a second etching step (S14) of further etching the silicon layer using the first processing gas. The second depositing step (S13) and the second etching step (S14) are alternately repeated at least two times each.