A particle beam irradiation apparatus includes an accelerator that extracts a pulse-shaped particle beam, a switching system that has a function of switching a particle beam in order not to be irradiated onto an irradiation subject, a database in which time dependency of the number of particles in one pulse of the particle beam is stored in accordance with a driving condition for the accelerator, a computing processing unit that calculates a timing of switching operation by the switching system, based on a desired accumulated number of particles to be irradiated onto the irradiation subject and the time dependency of the number of particles in one pulse of the particle beam, that is stored in the database, and a switching controller that controls the switching system based on the timing of switching operation by the switching system, that is calculated by the computing processing unit.
