A method of etching a copper layer of a target object including, on the copper layer, a mask having a pattern to be transferred onto the copper layer is provided. The method includes etching the copper layer by using plasma of a first gas containing a hydrogen gas; and processing the target object by using plasma of a second gas containing a hydrogen gas and a gas (hereinafter, referred to as “deposition gas”) that is deposited on the target object. Further, the etching of the copper layer by using plasma of the first gas and the processing of the target object by using plasma of the second gas are repeated alternately.