1. A fluoroscopy apparatus comprising: an illumination portion having a light source that radiates illumination light and excitation light onto a subject; a fluorescence-imaging unit that acquires a fluorescence image by imaging fluorescence generated at the subject by the radiation of the excitation light from the illumination portion; a return-light imaging unit that acquires a reference image by imaging return light returning from the subject by the radiation of the illumination light from the illumination portion; and an image-correction unit that corrects the fluorescence image acquired by the fluorescence-imaging unit by using the reference image acquired by the return-light imaging unit, wherein in the image-correction unit, a correction fluorescence image is obtained by raising a luminance value of the fluorescence image to the power of the reciprocal of a first exponent that is obtained by a power approximation of a characteristic of luminance versus distance from the illumination portion to the subject, for the fluorescence image acquired by the fluorescence-imaging unit when the excitation light of a prescribed intensity is radiated towards the subject; a correction reference image is obtained by raising a luminance value of the reference image to the power of the reciprocal of a second exponent that is obtained by a power approximation of a characteristic of luminance versus distance from the illumination portion to the subject, for the reference image obtained by the return-light imaging unit when the illumination light of a prescribed intensity is radiated towards the subject; and a corrected fluorescence image is obtained by dividing the correction fluorescence image by the correction reference image.