A plasma processing device includes a susceptor, processing vessel, dielectric plate, antenna, and projection. The susceptor has a stage surface on which a target object is to be arranged. The processing vessel accommodates the susceptor and has an opening in a side which opposes the stage surface of the susceptor. The dielectric plate closes the opening of the processing vessel. The antenna supplies a high-frequency electromagnetic field into the processing vessel through the dielectric plate. The projection projects from a surface of the antenna which opposes the dielectric plate toward the dielectric plate. The projection is conductive at least at its surface. A plasma processing method is also disclosed.