Abstract: An ion implant apparatus which forms ions from an ion source into an ion beam to implant the ions into a target to be ion-implanted through an ion beam introduction tube. The ion implant apparatus comprises: radiation means for radiating an electron beam, the radiating means fixed on the ion beam introduction tube; and a target for being radiated by an electron beam, said target reflecting the electron beam to generate a reflectance beam, the electron beam causing a secondary electron beam to be emitted from the electron beam target, the electron beam target being formed so as to prevent the reflectance beam and the secondary electron beam from being directly radiated on the target to be ion-implanted. The apparatus can keep high energy electrons from the surface of a wafer thereby to prevent the wafer from being charged negatively, and can trap the high energy electrons in the measuring system thereby to decrease errors in measuring a number of dopant atoms.