Provided are a charged particle beam generation apparatus, a charged particle beam irradiation apparatus, a particle beam therapy system, and a charged particle beam generation apparatus operating method capable of implementing injection of a charged particle beam into a circular accelerator at an arbitrary timing by setting a normal operation period of a linear accelerator to be larger than a shortest period and securing a stability of the beam. In timing control of controlling injecting, accelerating, emitting, and decelerating processes of a synchrotron (200), after an end of the emitting process, a linear accelerator (111) is allowed to stop repetition of an operation based on an after-end-of-emitting-process timing signal to be in a stand-by state and is allowed to be start the repetition of the operation in a constant period based on a master signal.