An ion implanting apparatus is provided, which can accurately measure a quantity of atoms that are implanted. The ion implanting apparatus according to the present invention has an object to be measured, and the object to be measured is arranged in an irradiating range in which ions are irradiated. When atoms are implanted into an object to be processed by irradiating ions of a processing gas and neutralized particles thereof, the object to be measured is heated through the irradiation with the processing gas ions and the neutralized particles. A control unit determines a quantity of the atoms that are implanted into the object to be processed from the temperature of the object to be measured.