A device for plasma processing comprises a gas supply system for supplying a source gas necessary for creating a plasma, and an exhaust system for discharging the gas to reduce the pressure in a container, in which a plasma is generated to process an object. The container encloses a conducting stage for supporting an object to be processed, and the stage has a structure to which DC or high-frequency voltage is applied. The stage includes the cooling channel within it to cool the object to be processed. The material of the cooling channel has a high thermal conductivity to transfer heat from the stage to the cooling channel, and the material is highly insulative to isolate the coolant from the DC or high-frequency voltage is applied to the stage.