In a dry etching device comprising a first electrically grounded electrode plate and a second electrode plate opposite to the first electrode plate in a hollow space and supplied with a voltage of a predetermined frequency, a control electrode member is placed in the hollow space between the first and the second electrode plates and is connected to a d.c. voltage source for a controllable d.c. voltage. The etch rate is electrically adjustable to a desired rate by the d.c. voltage. The control electrode member may be a conductive rod projected into the hollow space or a conductive flat mesh substantially parallel to the first and the second electrode plates. Alternatively, the member may be an annular ring-shaped conductor surrounding the gas plasma developed between the first and the second electrode plates. Specimens to be etched may be placed on both of the electrode plates when the etch rate is adjusted to the desired rate by the use of the member.