The electromagnet mounting frame is characterized by including: a top plate for supporting the electromagnet； plural legs for sustaining the top plate； and a cable placement member fixed to the plural legs and placed below the top plate； wherein a cable placement portion in which a power cable for the electromagnet is to be placed so as to extend in a traveling direction of the charged particle beam, is formed between the cable placement member and the top plate； and wherein the cable placement portion has a cable placement width (widthwise inter-leg length) that is a length thereof in a direction perpendicular to the traveling direction of the charged particle beam, and that is longer than a width of the electromagnet in the direction perpendicular to the traveling direction of the charged particle beam.
