A particle beam therapy system that irradiates a charged particle beam, accelerated by an accelerator, emitted through a beam transport system and scanned by a scanning electromagnet, into an irradiation field conforming to the size and the depth of a diseased site of a patient, the particle beam therapy system comprising: an irradiation apparatus unit comprising the scanning electromagnet, an irradiation management apparatus that controls the scanning electromagnet by the means of a scanning electromagnet power source, based on a desired irradiation position coordinates (Pi) of the charged particle beam; a patient sensor adapted to detect the motion of a patient; and an interlock information inputting device said interlock information inputting device generating an interlock signal for stopping irradiation of the charged particle beam, when a contingency occurs, wherein the irradiation management apparatus scans the charged particle beam onto respective slices, of the diseased site, that are layers corresponding to kinetic energy levels, wherein the irradiation management apparatus is provided with a command value generator that outputs a control input signal (Io, Ir) to the scanning electromagnet power source; and a stop step storage memory that stores a stop step corresponding to the desired irradiation position coordinates (Pi) at which irradiation of the charged particle beam stops, when the interlock signal is generated by the interlock information inputting device, characterised in that: the interlock information inputting device comprises means for detecting that the motion of the patient exceeds a predetermined range from a signal detected by the patient sensor, means for detecting that the measured position coordinates (Ps) or the measured beam size (Ss) of the charged particle beam detected by a position monitor exceed an allowable value, a patient call button for the patient to inform that he has become ill, and an irradiation stop button; and when irradiation of the charged particle beam is resumed, the irradiation management apparatus performs an idle operation in which the scanning electromagnet power source is controlled with a charged particle beam unirradiated, from a start step, which is situated prior to a step in the slice at which irradiation of the charged particle beam stops corresponding to an initial desired irradiation position coordinates, to the stop step, and then irradiates the charged particle beam from the desired irradiation position coordinates (Pi) corresponding to the stop step. an irradiation apparatus unit comprising the scanning electromagnet, an irradiation management apparatus that controls the scanning electromagnet by the means of a scanning electromagnet power source, based on a desired irradiation position coordinates (Pi) of the charged particle beam; the interlock information inputting device comprises means for detecting that the motion of the patient exceeds a predetermined range from a signal detected by the patient sensor, means for detecting that the measured position coordinates (Ps) or the measured beam size (Ss) of the charged particle beam detected by a position monitor exceed an allowable value, a patient call button for the patient to inform that he has become ill, and an irradiation stop button; and