There is provided a plasma processing device. The plasma processing device comprises: a processing chamber; a partition plate that has an insulating property, and configured to partition a space in the processing chamber into a reaction chamber in which an object to be processed is mounted and a plasma generating chamber in which plasma is generated, wherein a first electrode is provided on a surface of the partition plate on the side of the plasma generating chamber, and the partition plate has a plurality of through holes formed for supplying active species contained in the plasma generated in the plasma generating chamber to the reaction chamber; a second electrode disposed in the plasma generating chamber so as to face the first electrode; and a power supply configured to supply high-frequency power obtained by phase-controlling and superimposing high-frequency powers of a plurality of frequencies to one of the first electrode and the second electrode when the plasma is generated in the plasma generating chamber.