An apparatus for superimposing a fluorescent image (IM F) of an object and a background image (IM B) to create a superimposed image, the apparatus comprising: a light irradiating unit configured to emit excitation light (L 1) toward the object during a first period and to stop the emission of the excitation light during a second period different from the first period; a capturing unit having a plurality of pixels that are two-dimensionally arranged and configured to capture an image of the object during each of the first period and the second period, and to output first image data and second image data, respectively; a coefficient setting unit configured to set a coefficient (m) for adjusting a luminance value of the background image in the superimposed image; an image processing unit configured to create fluorescent image data including the fluorescent image and background image data including the background image based on the first image data and the second image data; and an identification unit configured to identify fluorescent pixels, which are pixels constituting the fluorescent image, and non-fluorescent pixels, which are pixels other than the fluorescent pixels, among the plurality of pixels using the fluorescent image data, wherein the image processing unit is configured to calculate values, which are obtained by summing pixel values of the fluorescent pixels of the fluorescent image data and pixel values of the fluorescent pixels of the background image data at a ratio of 1:1, as pixel values of the fluorescent pixels of the superimposed image and calculate values, which are obtained by multiplying at least pixel values of the non-fluorescent pixels of the background image data by the coefficient (m), as pixel values of the non-fluorescent pixels of the superimposed image to create the superimposed image, characterized in that if the luminance of the fluorescent image in the fluorescent image data is greater than the luminance of the background image in the background image data, then the coefficient setting unit is configured to set the coefficient to a value greater than or equal to 0 and less than 1, and if the luminance of the fluorescent image in the fluorescent image data is less than the luminance of the background image in the background image data, then the coefficient setting unit is configured to set the coefficient to a value greater than or equal to 1. a light irradiating unit configured to emit excitation light (L 1) toward the object during a first period and to stop the emission of the excitation light during a second period different from the first period; a capturing unit having a plurality of pixels that are two-dimensionally arranged and configured to capture an image of the object during each of the first period and the second period, and to output first image data and second image data, respectively; a coefficient setting unit configured to set a coefficient (m) for adjusting a luminance value of the background image in the superimposed image; an image processing unit configured to create fluorescent image data including the fluorescent image and background image data including the background image based on the first image data and the second image data; and an identification unit configured to identify fluorescent pixels, which are pixels constituting the fluorescent image, and non-fluorescent pixels, which are pixels other than the fluorescent pixels, among the plurality of pixels using the fluorescent image data, wherein the image processing unit is configured to calculate values, which are obtained by summing pixel values of the fluorescent pixels of the fluorescent image data and pixel values of the fluorescent pixels of the background image data at a ratio of 1:1, as pixel values of the fluorescent pixels of the superimposed image and calculate values, which are obtained by multiplying at least pixel values of the non-fluorescent pixels of the background image data by the coefficient (m), as pixel values of the non-fluorescent pixels of the superimposed image to create the superimposed image, characterized in that if the luminance of the fluorescent image in the fluorescent image data is greater than the luminance of the background image in the background image data, then the coefficient setting unit is configured to set the coefficient to a value greater than or equal to 0 and less than 1, and if the luminance of the fluorescent image in the fluorescent image data is less than the luminance of the background image in the background image data, then the coefficient setting unit is configured to set the coefficient to a value greater than or equal to 1.