An apparatus for processing a substrate is provided. The apparatus for processing the substrate includes a housing having a process space, a gas supply unit to supply gas into the process space, a support unit including a chuck to support the substrate in the process space and a lower electrode to surround the chuck when viewed from a top, a temperature adjusting plate provided in the housing, a dielectric plate unit coupled to the temperature adjusting plate, and having a dielectric plate disposed in opposite to the substrate supported by the support unit in the process space, and an upper electrode unit coupled to the temperature adjusting plate, and having an upper electrode disposed in opposition to the lower electrode. The dielectric plate unit includes a first base disposed between the dielectric plate and the temperature adjusting plate.