A sample stage includes a metallic electrode block to which high-frequency power is supplied from a high-frequency power supply, a dielectric heat generation layer which is disposed on a top surface of the electrode block and in which a film-like heater receiving power and generating heat is disposed, a conductor layer which is disposed to cover the heat generation layer, a ring-like conductive layer which is disposed to surround the heat generation layer at an outer circumferential side of the heat generation layer and contacts the conductor layer and the electrode block, and an electrostatic adsorption layer which is disposed to cover the conductor layer and electrostatically adsorbs a sample. The conductor layer and the ring-like conductive layer have dimensions more than a skin depth of a current of the high-frequency power and the electrode block is maintained at a predetermined potential during processing of the sample.