PURPOSE: To make beam adjustment efficiently by furnishing a plurality of fluorescent boards of profile monitor, and providing a driving mechanism for driving these fluorescent boards.

CONSTITUTION: At the time of incident adjustment of beam, a plurality of fluorescent boards 1 are all inserted in a beam duct, and the beam position at the first turn is examined by observing the fluorescence 13. The result is compared with the beam locus at beam adjusting which was designed previously, and meantime the energization amounts of a deflecting electric magnet, auxiliary electric magnet, or bump electric magnet are adjusted. When that of the fluorescent boards which is irradiated with the beam, is drawn off, the beam passes through it to run against the next profile monitor fluorescent board. Thereafter the boards are drawn off in the same manner while the energization amount of each electric magnet is adjusted, and then the beam will rotate round the accelerator for one turn. The beam having launched into the second turn will again run against the first profile monitor fluorescent board. Now the energization amounts of the electric magnets are again adjusted, and that fluores cent board which is irradiated with the beam is drawn off. Thus adjustment of beam locus can be made while the beam position after the second turn at the time of beam incidence, so that the efficincy of beam adjustment is enhanced.