An image capturing device includes an image capturing unit, a moving unit, a detector, and a determiner. The image capturing unit includes an optical transmission member; and a sensor capturing an image of the subject via the optical transmission member. The moving unit moves the image capturing unit in an optical axis direction of the sensor. The detector detects a contamination from first and second images. The first and second images are captured by the sensor when the image capturing unit is located at first and second positions in the optical axis direction, respectively. The second position is spaced away from the subject than the first position in the optical axis direction. The determiner determines that a contamination is deposited on the optical transmission member when a difference in the number of pixels in which a contamination is detected between the first and second images is less than a threshold.