A synchrotron injector system comprising a first ion source which generates a first ion, a second ion source which generates a second ion having a smaller charge-to-mass ratio than a charge-to-mass ratio of the first ion, a pre-accelerator having the capability to enable to accelerate both the first ion and the second ion, a low-energy beam transport line which is constituted in such a way to inject either the first ion or the second ion into the pre-accelerator, and a self-focusing type post-accelerator which accelerates only the first ion after acceleration which is emitted from the pre-accelerator.
