A plasma etching device comprising: a processing chamber having a closed space; a platen which is disposed in the processing chamber, on which a substrate is placed, and which is formed so that a peripheral portion thereof extends outward beyond the substrate placed; chucking means chucking the substrate placed on the platen and fixing it; gas supply means supplying a processing gas into the processing chamber; plasma generating means generating plasma from the processing gas supplied into the processing chamber; exhaust means exhausting a gas within the processing chamber to thereby reduce the pressure inside the processing chamber; power supply means supplying RF power to the platen; a protective member (31, 60) which is formed in an annular and plate-like shape and is configured to be capable of being placed on the peripheral portion of the platen, and which, when placed on the peripheral portion of the platen, covers an upper surface of a peripheral edge portion of the substrate with an inner peripheral edge portion thereof; support means (35, 65) disposed in the processing chamber for supporting the protective member (31, 60); lifting means which lifts up and down either one of the platen and the support means (35, 65) and which places the protective member (31, 60) supported by the support means (35, 65) onto the peripheral portion of the platen while lifting up and down it; and the protective member (31, 60) having at least three first protrusions (33, 61) formed on a first pitch circle on a lower surface thereof, the first protrusions (33, 61) being engaged in point contact with the peripheral portion of the platen when the protective member (31, 60) is placed onto the platen, and the first pitch circle being set so that its center is co-axial with a central axis of the protective member (31, 60); characterized in that the protective member (31, 60) is configured so that, when it is placed on the peripheral portion of the platen, a gap is formed between the protective member (31, 60) and the substrate on the platen without a contact portion between them. a processing chamber having a closed space; a platen which is disposed in the processing chamber, on which a substrate is placed, and which is formed so that a peripheral portion thereof extends outward beyond the substrate placed; chucking means chucking the substrate placed on the platen and fixing it; gas supply means supplying a processing gas into the processing chamber; plasma generating means generating plasma from the processing gas supplied into the processing chamber; exhaust means exhausting a gas within the processing chamber to thereby reduce the pressure inside the processing chamber; power supply means supplying RF power to the platen; a protective member (31, 60) which is formed in an annular and plate-like shape and is configured to be capable of being placed on the peripheral portion of the platen, and which, when placed on the peripheral portion of the platen, covers an upper surface of a peripheral edge portion of the substrate with an inner peripheral edge portion thereof; support means (35, 65) disposed in the processing chamber for supporting the protective member (31, 60); lifting means which lifts up and down either one of the platen and the support means (35, 65) and which places the protective member (31, 60) supported by the support means (35, 65) onto the peripheral portion of the platen while lifting up and down it; and the protective member (31, 60) having at least three first protrusions (33, 61) formed on a first pitch circle on a lower surface thereof, the first protrusions (33, 61) being engaged in point contact with the peripheral portion of the platen when the protective member (31, 60) is placed onto the platen, and the first pitch circle being set so that its center is co-axial with a central axis of the protective member (31, 60);