A fluorescence viewing device comprising: excitation light supply means for providing supply of excitation light for fluorescence observation to an observed object and which is capable of implementing ON/OFF switching of supply of the excitation light; a first imaging means of a progressive readout type for capturing an image of the observed object and alternately outputting a first frame image and a second frame image in a time series, as resultant image data of the observed object; image storage means for storing either the first frame image or the second frame image output from the first imaging means; and difference image generation means for generating a difference image by taking a difference respectively between one of the first frame image and the second frame image output from the first imaging means and respectively the other of the first frame image and the second frame image stored in the image storage means, wherein the excitation light supply means switches the supply of the excitation light so that one of an image acquisition period of the first frame and an image acquisition period of the second frame defined by the first imaging means is a fluorescence image acquisition period of a fluorescence image with the supply of the excitation light ON and the other is a background image acquisition period of a background image with the supply of the excitation light OFF, and a control device for controlling both the excitation light supply means and the first imaging means; wherein in the first imaging means, an exposure time of the fluorescence image acquisition period and an exposure time of the background image acquisition period are different from each other, the fluorescence viewing device further comprising: image processing means for performing correction for at least one of a brightness of the fluorescence image or a brightness of the background image, based on a ratio of the exposure time of the fluorescence image acquisition period and the exposure time of the background image acquisition period. excitation light supply means for providing supply of excitation light for fluorescence observation to an observed object and which is capable of implementing ON/OFF switching of supply of the excitation light; a first imaging means of a progressive readout type for capturing an image of the observed object and alternately outputting a first frame image and a second frame image in a time series, as resultant image data of the observed object; image storage means for storing either the first frame image or the second frame image output from the first imaging means; and difference image generation means for generating a difference image by taking a difference respectively between one of the first frame image and the second frame image output from the first imaging means and respectively the other of the first frame image and the second frame image stored in the image storage means, wherein the excitation light supply means switches the supply of the excitation light so that one of an image acquisition period of the first frame and an image acquisition period of the second frame defined by the first imaging means is a fluorescence image acquisition period of a fluorescence image with the supply of the excitation light ON and the other is a background image acquisition period of a background image with the supply of the excitation light OFF, and a control device for controlling both the excitation light supply means and the first imaging means; wherein in the first imaging means, an exposure time of the fluorescence image acquisition period and an exposure time of the background image acquisition period are different from each other, the fluorescence viewing device further comprising: image processing means for performing correction for at least one of a brightness of the fluorescence image or a brightness of the background image, based on a ratio of the exposure time of the fluorescence image acquisition period and the exposure time of the background image acquisition period.