Aimed at providing an ion implantation apparatus elongated in period over which failure of a target work, due to deposition and release of ion species typically to and from the inner surface of a through-hole shaping a beam shape of ion beam, may be avoidable, reduced in frequency of exchange of an aperture component, and consequently improved in productivity, an aperture component shaping a beam shape has a taper opposed to the ion beam, in at least a part of inner surface of at least the through-hole, and has a thick thermal-sprayed film formed so as to cover the inner surface and therearound of the through-hole.