An image acquisition system 1 includes: a light source 3 which outputs illumination light; an optical scanner 7 which scans a sample S with the illumination light; an optical scanner control unit 9; a detection optical system 15, 17 which focuses fluorescence from the sample S; an imaging device 19 which has a light receiving surface 19c in which a plurality of pixel rows 19d are arranged, and an imaging control section 19b, and which can perform signal readout of each of the plurality of pixel rows 19d from the light receiving surface 19c; and a calculation unit 21 which calculates an interval of signal readout between adjacent pixel rows 19d, based on a moving speed of an illuminated region on the light receiving surface 19c; the imaging control section 19b controls signal readout of each pixel row 19d, based on the interval of the signal readout thus calculated.