The objective of the present invention is to accurately calculate a beam irradiation position even when the relative positions of a scanning electromagnet and a position monitor change and to implement high-accuracy beam irradiation. There are provided a position monitor (9) that detects a passing position of a charged particle beam (2) and an irradiation control apparatus (23) that calculates a distance (D) from a predetermined reference point to the position monitor (9), calculates a beam irradiation position (P) on an irradiation subject (25), and controls irradiation of the beam (2). The irradiation control apparatus (23) includes a position calculation apparatus (30) that calculates the beam irradiation position (P), based on a beam position (Pm) detected by the position monitor (9), a scanning starting point distance information on a distance from a irradiation plane (31) of the irradiation subject (25) to a scanning starting point (1x, 1y), of the beam (2), in a scanning electromagnet (5x, 5y), and a position monitor distance information on a distance, from the irradiation plane (31) to the position monitor (9), that is calculated based on the calculated distance (D).
