A collation device includes a light source unit; a camera unit that receives light emitted from the light source unit and reflected in a collation area of an object to acquire a photographed image of the collation area; and a processor configured to, by executing a program: detect a positional relationship between the light source unit and the camera unit by using the photographed image, and notify of a collation result between the photographed image and a registered image prepared in advance by using the positional relationship.