To provide an ion implantation device which suppresses diffusion of an ion beam, can finely control a scanning waveform and can obtain a large scanning angle of about 10.degree..In the ion implantation device, first, second and third chambers 12A, 14A and 16A are arranged in predetermined places on a beam line, first and second gaps 20A and 22A intervene between the first chamber 12A and the second chamber 14A and between the second chamber 14A and the third chamber 16A, the second chamber 14A is electrically insulated from the first and third chambers 12A and 16A via first and second electrode pairs 26A and 28A attached to the first and second gaps 20A and 22A, respectively, the first and second electrode pairs 26A and 28A obliquely cross a standard axis J of the ion beam at a predetermined angle in opposite directions, and the second chamber 14 is connected to a scanning power source 40A which applies an electric potential having desired scanning waveform.