At oxygen ion implanting steps in manufacture of a SIMOX wafer, a path is formed inside or on a back surface of wafer holding means, and oxygen ions are implanted while heating an outer peripheral portion of the wafer that is in contact with the wafer holding means by flowing a heated fluid through this path. An in-plane temperature of a wafer held at the time of ion implantation is prevented from becoming uneven, and in-plane film thicknesses of both an SOI layer and a BOX layer are uniformed.