An electron cyclotron resonance ion generator includes a vacuum-tight chamber configured to contain a plasma, a magnetic field generator configured to generate a magnetic field in the chamber, a waveguide configured to propagate a high-frequency wave inside the chamber, a first ionization stage located at one end of the chamber, the first stage including an ionization zone in which ions are generated, the magnetic field being approximately parallel to a longitudinal axis in the ionization zone, a second magnetic confinement stage for the ions generated in the ionization zone, the second stage using a first high-frequency wave being propagated in the chamber from the waveguide, the magnetic field being approximately parallel to the longitudinal axis between the ionization zone and the second confinement stage, such that the ions generated in the ionization zone migrate towards the second confinement stage and the first and second stages contain the same continuous plasma.