Provided is an imaging system that can prevent exposure unevenness in an image even though exposure and readout of an imaging element are performed with timing shifted for every line. An imaging system 1 includes: an illumination unit 41 that emits illumination light for illuminating a subject; a light receiving unit 244f in which pixels are arranged two-dimensionally, each pixel receiving light and generating an electric signal by performing photoelectric conversion of the light; a readout unit 244g that sequentially reads out the electric signal for every horizontal line from the light receiving unit 244f; and an illumination controller 42 that keeps intensity of the illumination light emitted from the illumination unit 41 constant in at least a part of a readout period where the readout unit 244g reads out the horizontal line of the light receiving unit 244f in one frame or one field period, and outside the readout period, variably controls an illumination time of the illumination light emitted from the illumination unit 41.