A particle beam irradiation apparatus (58, 61) that scans by means of a scanning electromagnet (10, 11) a charged particle beam accelerated by an accelerator and irradiates the charged particle beam onto an irradiation subject, the particle beam irradiation apparatus (58, 61) comprising: a detector (12a, 12b, 8, 9) that detects a measured irradiation position relevant value (PR measured) related to an irradiation position of the charged particle beam, and a display unit, a data processing apparatus (19, 28) configured to display on the display unit the measured irradiation position relevant value (PR measured) and an irradiation position relevant value error (PR error), which is an error of the measured irradiation position relevant value (PR measured) with respect to a desired irradiation position relevant value (PR desired) related to a desired irradiation position (P desired) of the charged particle beam, in such a way that the measured irradiation position relevant value (PR measured) and the irradiation position relevant value error (PR error) correspond to each other, wherein the data processing apparatus (19, 28) comprises; an input unit that receives the measured irradiation position relevant value (PR measured) and the desired irradiation position relevant value (PR desired); and a calculation unit that displays a desired value display figure (23, 27) indicating the desired irradiation position relevant value (PR desired) at the coordinates of the desired irradiation position relevant value (PR desired) and a measured value display figure (24, 26) indicating the measured irradiation position relevant value (PR measured) at display coordinates (PR def), which are coordinates obtained by adding the desired irradiation position relevant value (PR desired) to the coordinates acquired by arithmetically operating the irradiation position relevant value error (PR error) with deformation coefficients (k), when the desired value display figure (23, 27) and the measured value display figure (24, 26) are displayed in a display region which is the reproduction of an irradiation-region relevant region related to an irradiation region of the charged particle beam, and that displays a line that connects the measured value display figure (24, 26) with the desired value display figure (23, 27). wherein the calculation unit comprises; a measured value calculation unit that calculates the display coordinates (PR def) and displays the measured value display figure (24, 26) at the display coordinates (PR def); a desired value calculation unit that displays the desired value display figure (23, 27) at the coordinates of the desired irradiation position relevant value (PR desired); and a line display calculation unit that displays the line that connects the measured value display figure (24, 26) with the desired value display figure (23, 27). a detector (12a, 12b, 8, 9) that detects a measured irradiation position relevant value (PR measured) related to an irradiation position of the charged particle beam, and a display unit, a data processing apparatus (19, 28) configured to display on the display unit the measured irradiation position relevant value (PR measured) and an irradiation position relevant value error (PR error), which is an error of the measured irradiation position relevant value (PR measured) with respect to a desired irradiation position relevant value (PR desired) related to a desired irradiation position (P desired) of the charged particle beam, in such a way that the measured irradiation position relevant value (PR measured) and the irradiation position relevant value error (PR error) correspond to each other, wherein the data processing apparatus (19, 28) comprises; an input unit that receives the measured irradiation position relevant value (PR measured) and the desired irradiation position relevant value (PR desired); and a calculation unit that displays a desired value display figure (23, 27) indicating the desired irradiation position relevant value (PR desired) at the coordinates of the desired irradiation position relevant value (PR desired) and a measured value display figure (24, 26) indicating the measured irradiation position relevant value (PR measured) at display coordinates (PR def), which are coordinates obtained by adding the desired irradiation position relevant value (PR desired) to the coordinates acquired by arithmetically operating the irradiation position relevant value error (PR error) with deformation coefficients (k), when the desired value display figure (23, 27) and the measured value display figure (24, 26) are displayed in a display region which is the reproduction of an irradiation-region relevant region related to an irradiation region of the charged particle beam, and that displays a line that connects the measured value display figure (24, 26) with the desired value display figure (23, 27). a measured value calculation unit that calculates the display coordinates (PR def) and displays the measured value display figure (24, 26) at the display coordinates (PR def); a desired value calculation unit that displays the desired value display figure (23, 27) at the coordinates of the desired irradiation position relevant value (PR desired); and a line display calculation unit that displays the line that connects the measured value display figure (24, 26) with the desired value display figure (23, 27).