A target image capturing device according to an aspect of the present disclosure includes: a delay circuit configured to receive a timing signal from outside and output a first trigger signal at a timing delayed by a first delay time from the reception of the timing signal; an illumination light source configured to emit light based on the first trigger signal; an image capturing unit disposed to capture an image of a shadow of a target to be observed, which is generated when the target is irradiated with the light emitted from the illumination light source; a processing unit configured to perform image processing including processing of measuring a background luminance from the image captured by the image capturing unit; and a control unit configured to perform control to adjust the first delay time based on the background luminance.