An identification device configured to perform authenticity determination on an article with an anti-counterfeit medium attached, the identification device comprising: an observation object shape frame display configured to display, on a display screen, an observation object shape image indicating a shape of the anti-counterfeit medium observed at an observation angle, and display image data that is an image of an imaging object of an image-capturing device, the anti-counterfeit medium being designed such that an observed pattern of light varies as the observation angle varies; a shape similarity calculator configured to calculate a shape similarity between the observation object shape image and an outer shape of the anti-counterfeit medium serving as the imaging object on the display screen; and an imaging determinator configured to perform imaging determination as to whether or not the observation angle and an observation position of the image-capturing device are correct based on whether or not the shape similarity is equal to or greater than a preset shape similarity threshold; characterized in that the shape similarity calculator is configured to calculate a ratio between a gradation of a first color tone of a first predetermined pixel of the image of the imaging object and a gradation of a second color tone of a second predetermined pixel of the image of the imaging object, compare the calculated ratio with a predetermined ratio, adapt the image of the imaging object such that a difference between the calculated ratio and the predetermined ratio is absorbed under an assumption that the difference is caused by a difference in an illumination light illuminating the imaging object to obtain the image of the imaging object and an illumination light used to obtain the observation object shape image, and use the adapted image of the imaging object for the calculating of the shape similarity; wherein the second color tone is different from the first color tone; and the second pixel is different from the first pixel. an observation object shape frame display configured to display, on a display screen, an observation object shape image indicating a shape of the anti-counterfeit medium observed at an observation angle, and display image data that is an image of an imaging object of an image-capturing device, the anti-counterfeit medium being designed such that an observed pattern of light varies as the observation angle varies; a shape similarity calculator configured to calculate a shape similarity between the observation object shape image and an outer shape of the anti-counterfeit medium serving as the imaging object on the display screen; and an imaging determinator configured to perform imaging determination as to whether or not the observation angle and an observation position of the image-capturing device are correct based on whether or not the shape similarity is equal to or greater than a preset shape similarity threshold; characterized in that the shape similarity calculator is configured to calculate a ratio between a gradation of a first color tone of a first predetermined pixel of the image of the imaging object and a gradation of a second color tone of a second predetermined pixel of the image of the imaging object, compare the calculated ratio with a predetermined ratio, adapt the image of the imaging object such that a difference between the calculated ratio and the predetermined ratio is absorbed under an assumption that the difference is caused by a difference in an illumination light illuminating the imaging object to obtain the image of the imaging object and an illumination light used to obtain the observation object shape image, and use the adapted image of the imaging object for the calculating of the shape similarity; wherein the second color tone is different from the first color tone; and the second pixel is different from the first pixel.