To prevent variation of secondary electrons reaching a semiconductor wafer and surely neutralizing the charging of the semiconductor wafer upon ion implantation, to prevent charge up.

The electron shower device comprises a disk 6, on which a semiconductor wafer 7 is mounted, a filament assembly 1 which generates primary electrons 8 in a direction perpendicular to an ion beam 11, a target 2 which surrounds the path of the ion beam 11 and causes the primary electrons 8 to strike an inner wall to generate secondary electrons 9, a bias aperture 5 applied by prescribed negative voltage for facilitating the arrival of the secondary electrons 9 on the side of the semiconductor wafer 7, a tilt bellows 3 which surrounds the target 2, and a secondary electron detecting part 10 which detects the secondary electrons 9. A suppressor 4 for transfer of the secondary electrons applied by the negative voltage for supplying the secondary electrons 9 as set to the semiconductor water 7 is provided about the target 2 inside the tilt bellows 3.