An image acquisition device comprising: a stage for mounting a sample; a light source for emitting light to the sample; a lightguide optical system including an objective lens arranged so as to oppose the sample on the stage; an image pickup element for capturing an optical image of the sample guided by the lightguide optical system; a focus calculation unit for calculating focus information of the sample according to image data from the image pickup element; a first drive unit for moving a field position of the objective lens with respect to the sample; a second drive unit for changing a focal position of the objective lens with respect to the sample; and a controller for controlling the image pickup element, first drive unit, and second drive unit; wherein the image pickup element is a two-dimensional image pickup element having a plurality of pixel columns, adapted to perform rolling readout in which image data readout timings are varied among the pixel columns and readout start signals for the respective pixel columns are sequentially outputted with a predetermined time difference; and wherein the controller is configured to synchronize movement of a predetermined part of the sample within a field of the objective lens in a direction orthogonal to the optical axis of the objective lens, caused by the first drive unit, with the rolling readout of the image pickup element such that each pixel column of the image pickup element is exposed to an optical image of the predetermined part in the sample, while causing the second drive unit to change the focal position of the objective lens with respect to the sample. a stage for mounting a sample; a light source for emitting light to the sample; a lightguide optical system including an objective lens arranged so as to oppose the sample on the stage; an image pickup element for capturing an optical image of the sample guided by the lightguide optical system; a focus calculation unit for calculating focus information of the sample according to image data from the image pickup element; a first drive unit for moving a field position of the objective lens with respect to the sample; a second drive unit for changing a focal position of the objective lens with respect to the sample; and a controller for controlling the image pickup element, first drive unit, and second drive unit; wherein the image pickup element is a two-dimensional image pickup element having a plurality of pixel columns, adapted to perform rolling readout in which image data readout timings are varied among the pixel columns and readout start signals for the respective pixel columns are sequentially outputted with a predetermined time difference; and wherein the controller is configured to synchronize movement of a predetermined part of the sample within a field of the objective lens in a direction orthogonal to the optical axis of the objective lens, caused by the first drive unit, with the rolling readout of the image pickup element such that each pixel column of the image pickup element is exposed to an optical image of the predetermined part in the sample, while causing the second drive unit to change the focal position of the objective lens with respect to the sample.