A determination system comprising: an imaging data acquisition device that is configured to capture an image of a printed surface of a printed product to acquire imaging data of the captured image; and a determination device that is configured to determine, based on the imaging data acquired by the imaging data acquisition device, a printing method used to produce the printed surface of the printed product for which the image is captured by the imaging data acquisition device, wherein the determination device is further configured to select a determination area included in the captured image from the imaging data acquired by the imaging data acquisition device, extract a determination image of a preset target color from the selected determination area, binarize gradation data of the target color in a plurality of pixel regions constituting the extracted determination image by using as a reference a binarization threshold suitable for each determination area to acquire binarized reference binary data of the determination image, convert the gradation data of the target color in the plurality of pixel regions constituting the extracted determination image with respect to a dark portion of the determination image to acquire converted gradation data, binarize the acquired converted gradation data by using as a reference the binarization threshold to acquire comparison binary data, acquire, based on a comparison result obtained by comparing the reference binary data with the comparison binary data, a determination value for determining a printing method used to produce the printed surface of the printed product, and determine, based on the acquired determination value, a printing method used to produce the printed surface of the printed product. an imaging data acquisition device that is configured to capture an image of a printed surface of a printed product to acquire imaging data of the captured image; and a determination device that is configured to determine, based on the imaging data acquired by the imaging data acquisition device, a printing method used to produce the printed surface of the printed product for which the image is captured by the imaging data acquisition device, wherein the determination device is further configured to select a determination area included in the captured image from the imaging data acquired by the imaging data acquisition device, extract a determination image of a preset target color from the selected determination area, binarize gradation data of the target color in a plurality of pixel regions constituting the extracted determination image by using as a reference a binarization threshold suitable for each determination area to acquire binarized reference binary data of the determination image, convert the gradation data of the target color in the plurality of pixel regions constituting the extracted determination image with respect to a dark portion of the determination image to acquire converted gradation data, binarize the acquired converted gradation data by using as a reference the binarization threshold to acquire comparison binary data, acquire, based on a comparison result obtained by comparing the reference binary data with the comparison binary data, a determination value for determining a printing method used to produce the printed surface of the printed product, and determine, based on the acquired determination value, a printing method used to produce the printed surface of the printed product.