PROBLEM TO BE SOLVED: To provide a scanning endoscope system capable of generating an image with brightness suitable for observation.SOLUTION: A scanning endoscope system comprises: a light guiding part for guiding illumination light emitted from a light source a drive part for oscillating the light guiding part so that an irradiation position of the illumination light draws a locus corresponding to a spiral scanning pattern a light receiving part for receiving return light of the illumination light emitted to a subject a light detection part for outputting a signal corresponding to intensity of the return light a sampling part for acquiring the number of pixels according to a prescribed sampling period a pixel value generation part for generating a pixel value of each pixel to be acquired by the sampling part, by accumulating the signal to be output from the light detection part a calculation part for calculating an average of the pixel values of all pixels included in one area, on the basis of results of processing by the sampling part and the pixel value generation part and an illumination light amount adjusting part for changing or maintaining an amount of the illumination light at the time of illuminating the area, on the basis of a result of comparing the average with a brightness target value.
