An image acquisition device comprising: a stage that holds a sample; a light emission unit that emits instantaneous light; a light guide optical system that includes an objective lens disposed to face the sample on the stage; and a drive unit that moves the sample in a scanning direction intersecting an optical axis of the objective lens at a predetermined speed, a two-dimensional image capturing element that captures an optical image of the sample, which is guided by the light guide optical system, through lane scanning in cooperation with the light emission unit and the drive unit, and acquires observation image data constituted by a plurality of tile image rows; a control unit that controls execution of the lane scanning by the light emission unit, the drive unit, and the two-dimensional image capturing element; characterized in that the image acquisition device further comprises: a determination unit that counts the number of tile images included in each of the tile image rows which is acquired in one lane, and determines whether or not the number of images reaches a planned acquisition count that is set in advance, wherein in a case where the determination unit determines that the number of images does not reach the planned acquisition count, the control unit re-executes the lane scanning with respect to the one lane, and when re-executing the lane scanning, the control unit sets a movement speed of the stage to a speed slower than the predetermined speed. a stage that holds a sample; a light emission unit that emits instantaneous light; a light guide optical system that includes an objective lens disposed to face the sample on the stage; and a drive unit that moves the sample in a scanning direction intersecting an optical axis of the objective lens at a predetermined speed, a two-dimensional image capturing element that captures an optical image of the sample, which is guided by the light guide optical system, through lane scanning in cooperation with the light emission unit and the drive unit, and acquires observation image data constituted by a plurality of tile image rows; a control unit that controls execution of the lane scanning by the light emission unit, the drive unit, and the two-dimensional image capturing element; characterized in that the image acquisition device further comprises: a determination unit that counts the number of tile images included in each of the tile image rows which is acquired in one lane, and determines whether or not the number of images reaches a planned acquisition count that is set in advance, wherein in a case where the determination unit determines that the number of images does not reach the planned acquisition count, the control unit re-executes the lane scanning with respect to the one lane, and when re-executing the lane scanning, the control unit sets a movement speed of the stage to a speed slower than the predetermined speed. a determination unit that counts the number of tile images included in each of the tile image rows which is acquired in one lane, and determines whether or not the number of images reaches a planned acquisition count that is set in advance, wherein in a case where the determination unit determines that the number of images does not reach the planned acquisition count, the control unit re-executes the lane scanning with respect to the one lane, and when re-executing the lane scanning, the control unit sets a movement speed of the stage to a speed slower than the predetermined speed.