A tray 15 for a dry etching apparatus 1 has substrate accommodation holes 19A to 19D penetrating thickness direction and a substrate support portion 21 supporting an outer peripheral edge portion of a lower surface 2a of a substrate 2. A dielectric plate 23 has a tray support surface 28 supporting a lower surface of the tray 15, substrate placement portions 29A through 29D inserted from a lower surface side of the tray 15 into the substrate accommodation holes 19A through 19D and having a substrate placement surface 31 at its upper end surface for placing the substrate 2. A dc voltage applying mechanism 43 applies a dc voltage to an electrostatic attraction electrode 40. A heat conduction gas supply mechanism 45 supplies a heat conduction gas between the substrate 2 and substrate placement surface 31. The substrate 2 can be retained on the substrate placement surface 31 with high degree of adhesion. This results in that the cooling efficiency of the substrate 2 is improved and processing is uniformed at the entire region of the substrate surface including the vicinity of the outer peripheral edge.