PROBLEM TO BE SOLVED: To provide image acquisition device and a method for acquiring an image of a biological sample.SOLUTION: An image acquisition device includes a darkroom and a light source 34 that is provided inside the darkroom and irradiates a biological sample 21 held inside the darkroom with infrared light. The image acquisition device further includes an image acquisition unit that acquires a bright field image 41 of the biological sample 21 in an illuminated state where the biological sample 21 is irradiated with the infrared light and acquires a weak light image of the biological sample 21 in a non-illuminated state, and a control device 12 that has a display unit 13 displaying the bright field image 41 and the weak light image 42 overlapped with each other.
