PURPOSE: To effect ion implantation also for the rear of a wafer by rotating the whole of a platen of an ion implantation device or the platen and a wafer holder by providing a through-hole through the platen and further providing a rotary shaft on the platen or on the wafer holder.

CONSTITUTION: An implantation chamber 2 of an ion implantation device includes a wafer holder 7 with a rotary shaft, and a platen 8 having a through- hole 9 therethrough. A wafer 1 carried from a pre-chamber is placed on the platen 8 and is held by the holder 7, permitting an edge portion thereof to be fixed. Upon ion implantation for the rear of the wafer 1, the platen 8 and the whole of the holder are rotated 180° by a platen reversing rotary shaft fixed to the platen 8 and the holder 7. The second rotary shaft 13 for implantation for the rear is located at a position of the first rotary shaft 11, and the device is operated through the shaft 13 to ion implant the back surface of the wafer.