Abstract: A plasma processing method of etching a ruthenium-containing film using a first etching process (S01) and a subsequent second etching process (S02). S02 comprises a first step (S11) where a modified layer is formed on the surface of the ruthenium-containing film using a halogen element-containing plasma, and a following second step (S12) to desorb the modified layer using a plasma generated with an oxygen element-containing gas; S11 and S12 are repeated alternately.