The technical solution of the present disclosure provides an ion generator for dissociating sample ions for the second time by laser, of which the dissociation efficiency is further improved with a lower cost. The ion generator includes: a desorption device configured to desorb sample particles into a pre-determined area; a light source emitting a light beam and focusing the light beam to the pre-determined area, thereby ionizing, fragmenting or atomizing the sample particles in the pre-determined area; and a focusing reflector for reflecting the light beam that is emitted by the light source and travels through the pre-determined area, and focusing the light beam to the pre-determined area, thereby ionizing, fragmenting or atomizing the sample particles in the pre-determined area at least once again, during which each time the light beam is reflected on the surface of the focusing reflector, the light beam is focused to the pre-determined area correspondingly.