A particle beam irradiation apparatus There is provided a data processing apparatus that displays on a display unit a measured irradiation position value and an irradiation position value error, which is the error of the measured irradiation position relevant value related to the irradiation position of charged particle beam with respect to a desired irradiation position value related to a desired irradiation position, so that the measured irradiation position relevant value and the irradiation position relevant value error correspond to each other. The data processing apparatus displays a desired value display figure indicating a desired irradiation position relevant value at the coordinates of the desired irradiation position value and a measured value display figure at display coordinates, which are coordinates obtained by adding the desired irradiation position value to the coordinates acquired by arithmetically operating an irradiation position value error with deformation coefficients, and displays a line that connects the measured value display figure with the desired value display figure.