A high-frequency acceleration type ion acceleration and transportation apparatus is a beamline after an ion beam is accelerated by a high-frequency acceleration system having an energy spread with respect to set beam energy and includes an energy analysis deflection electromagnet and a horizontal beam focusing element. In the ion acceleration and transportation apparatus, a double slit that is configured by an energy spread confining slit and an energy analysis slit is additionally disposed at a position at which energy dispersion and a beam size are to be appropriate. The position is determined based on a condition of the energy analysis deflection electromagnet and the horizontal beam focusing element, and the double slit performs energy separation and energy definition and decreases the energy spread of the ion beam by performing adjustment for a smaller energy spread while suppressing a decrease in the amount of a beam current.