A plasma etching apparatus comprising: a chamber which comprises a cylindrical body portion, a top plate for closing the top of the body portion, and a bottom plate for closing the bottom of the body portion, and which has a plasma generating space defined in an upper region in the body portion and a processing space defined below the plasma generating space; a coil disposed on the outside of a portion of the chamber corresponding to the plasma generating space in such a manner that it winds around the chamber; a platen which is disposed in the processing space in the chamber and on which a substrate to be processed is to be placed; processing gas supply means for supplying a processing gas into the plasma generating space in the chamber; power supply means for the coil configured to supply RF power to the coil; power supply means for the platen configured to supply RF power to the platen; and a plasma density adjusting member which comprises a cylindrical member having an opening at the top and an opening at the bottom, and the upper end portion of which is fixed on an inner wall of the chamber between the plasma generating space and the platen, and which adjusts the in-plane density of a plasma generated in the plasma generating space and guides the plasma to a substrate on the platen, the body portion forming the plasma generating space is formed to have an inner diameter larger than the outer dimension of the substrate, and the plasma density adjusting member is made of a conductive material and is formed in a funnel shape the lower end portion of which has an inner diameter smaller than the inner diameter of the upper end portion thereof and than the inner diameter of the body portion forming the plasma generating space, characterized in that the plasma density adjusting member is made of a conductive material grounded; and a plane defined by the upper end portion and a plane defined by the lower end portion of the plasma density adjusting member are substantially parallel with each other and an angle formed by the planes and a funnel-shaped surface of the plasma density adjusting member is within a range of 59 to 81 degrees. a chamber which comprises a cylindrical body portion, a top plate for closing the top of the body portion, and a bottom plate for closing the bottom of the body portion, and which has a plasma generating space defined in an upper region in the body portion and a processing space defined below the plasma generating space; a coil disposed on the outside of a portion of the chamber corresponding to the plasma generating space in such a manner that it winds around the chamber; a platen which is disposed in the processing space in the chamber and on which a substrate to be processed is to be placed; processing gas supply means for supplying a processing gas into the plasma generating space in the chamber; power supply means for the coil configured to supply RF power to the coil; power supply means for the platen configured to supply RF power to the platen; and a plasma density adjusting member which comprises a cylindrical member having an opening at the top and an opening at the bottom, and the upper end portion of which is fixed on an inner wall of the chamber between the plasma generating space and the platen, and which adjusts the in-plane density of a plasma generated in the plasma generating space and guides the plasma to a substrate on the platen, the body portion forming the plasma generating space is formed to have an inner diameter larger than the outer dimension of the substrate, and the plasma density adjusting member is made of a conductive material and is formed in a funnel shape the lower end portion of which has an inner diameter smaller than the inner diameter of the upper end portion thereof and than the inner diameter of the body portion forming the plasma generating space, characterized in that the plasma density adjusting member is made of a conductive material grounded; and a plane defined by the upper end portion and a plane defined by the lower end portion of the plasma density adjusting member are substantially parallel with each other and an angle formed by the planes and a funnel-shaped surface of the plasma density adjusting member is within a range of 59 to 81 degrees.