PURPOSE: To display a beam cross-section image which can be inferred easily by reconfiguring a beam integration pattern which is measured by a profile monitor and then displaying an obtained two-dimensional beam section image.

CONSTITUTION: A data indicating an integration pattern of a beam 30 which is measured by a three-line type profile monitor 20 is supplied to a beam section image reconfiguration and display device 10. Namely, a head 22 is driven by an air cylinder 21 so that wires 22x-22z scan a section of the beam 30 within a measurement plane 31 which is vertical to an irradiation direction of the beam 30, thus enabling an integration pattern of beam current in three directions to be measured. A signal indicating the beam current integration pattern in three directions from the monitor 20 is supplied to the device 10. Then, in the device 10, a section image within the measurement plane 31 which is vertical to the irradiation direction of the beam 30 is reconfigured by a neural network 11 and the section image of the beam 30 is displayed on a CRT display 40.