A processing device, comprising: (a) a base for holding a processing target, wherein said base is a ceramic body providing a substrate mounting surface for mounting of the processing target thereon, a back surface on its opposite side from said substrate mounting surface, and an outer circumferential surface connecting said substrate mounting surface to said back surface, and said base has a plurality of linear gas-providing passages (21a, 21b, 21c) formed in said base, each of said plurality of linear gas-providing passages (21a, 21b, 21c) being connected to an end opening at said outer circumferential surface of said base and having a circular cross section which is surrounded by material of said ceramic body; and (b) a tubular member bonded to said back surface of said base, wherein said tubular member has a plurality of gas introduction passages; wherein each of said plurality of gas introduction passages is connected through a gas coupling passage formed at said back surface of said base to a linear gas-providing passage (21a, 21b) of said plurality of linear gas-providing passages (21a, 21b, 21c) for supply of gas thereto; wherein said plurality of linear gas-providing passages (21a, 21b, 21c) is connected to a coupling passage which couples said plurality of linear gas-providing (21a, 21b, 21c) to each other, said coupling passage being a groove formed in said back surface of said base; and wherein each linear gas-providing passage (21a, 21b) of said plurality of linear gas-providing passages (21a, 21b, 21c) which is connected to a gas coupling passage is connected to said coupling passage through said gas coupling passage and each linear gas-providing passage of said plurality of linear gas-providing passages (21a, 21b, 21c) which is not connected to a gas coupling passage is connected to said coupling passage through a coupling passage part. (a) a base for holding a processing target, wherein said base is a ceramic body providing a substrate mounting surface for mounting of the processing target thereon, a back surface on its opposite side from said substrate mounting surface, and an outer circumferential surface connecting said substrate mounting surface to said back surface, and said base has a plurality of linear gas-providing passages (21a, 21b, 21c) formed in said base, each of said plurality of linear gas-providing passages (21a, 21b, 21c) being connected to an end opening at said outer circumferential surface of said base and having a circular cross section which is surrounded by material of said ceramic body; and (b) a tubular member bonded to said back surface of said base, wherein said tubular member has a plurality of gas introduction passages; wherein each of said plurality of gas introduction passages is connected through a gas coupling passage formed at said back surface of said base to a linear gas-providing passage (21a, 21b) of said plurality of linear gas-providing passages (21a, 21b, 21c) for supply of gas thereto; wherein said plurality of linear gas-providing passages (21a, 21b, 21c) is connected to a coupling passage which couples said plurality of linear gas-providing (21a, 21b, 21c) to each other, said coupling passage being a groove formed in said back surface of said base; and wherein each linear gas-providing passage (21a, 21b) of said plurality of linear gas-providing passages (21a, 21b, 21c) which is connected to a gas coupling passage is connected to said coupling passage through said gas coupling passage and each linear gas-providing passage of said plurality of linear gas-providing passages (21a, 21b, 21c) which is not connected to a gas coupling passage is connected to said coupling passage through a coupling passage part.