An image acquisition device comprising: a stage for mounting a 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 focus map producing unit for producing a focus map of the sample according to the focus information; 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 respective readout operations for the pixel columns are sequentially performed with a predetermined time difference; wherein the controller is arranged to control the first and second drive units so as to reciprocate the focal position of the objective lens with respect to the sample in an optical axis direction of the objective lens while moving the field position of the objective lens with respect to the sample and acquires the image data by synchronizing the field position movement with the rolling readout of the image pickup element; and wherein the focus map producing unit is arranged to produce the focus map according to a plurality of pieces of the focus information calculated by the focus calculation unit. a stage for mounting a 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 focus map producing unit for producing a focus map of the sample according to the focus information; 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 respective readout operations for the pixel columns are sequentially performed with a predetermined time difference; wherein the controller is arranged to control the first and second drive units so as to reciprocate the focal position of the objective lens with respect to the sample in an optical axis direction of the objective lens while moving the field position of the objective lens with respect to the sample and acquires the image data by synchronizing the field position movement with the rolling readout of the image pickup element; and wherein the focus map producing unit is arranged to produce the focus map according to a plurality of pieces of the focus information calculated by the focus calculation unit.