A target object detection device capable of providing an image useful for discovering a target object from an aerial image is provided. A target object detection device for detecting at least one target object from an aerial image is provided with an imaging device, a computer, and a display device. The computer is configured to divide the first aerial image into a plurality of first images, output a confidence score that the target object is included, for each of the plurality of first images, and cause the display device to display a first discrimination image capable of discriminating a degree of the confidence score and a portion of the first aerial image corresponding to the confidence score.