In an ion implanting apparatus and a method for implanting ions are provided. The ion implanting apparatus includes an ion source part, a substrate holding part, a beam current adjusting part, a doping quantity measuring part, and an ion beam control part. The ion source part generates an ion beam. The ion beam is irradiated onto the substrate and the ions are implanted into the substrate. The beam current adjusting part is disposed between the ion source part and the substrate holding part, to adjust a beam current. The doping quantity measuring part is disposed on substantially the same surface as the substrate, to measure ion doping quantity. The ion beam control part is connected to the doping quantity measuring part, to control the ion source part and the beam current adjusting part.