1. An image photographing device photographing an image through a front camera and a rear camera, the image photographing device comprising: a display; a feature extractor configured to extract facial features from an image of a user's face displayed on a preview screen through the rear camera; a structure extractor configured to extract a structure of the user's face by using the extracted facial features; an expression extractor configured to extract an expression of the user by using the extracted facial features if the extracted structure of the face matches a standard facial structure; and an alarm configured to output a photographing notification signal if the extracted expression of the user matches a standard facial expression, wherein the expression extractor is further configured to: extract a closed curve of an eye region and a closed curve of a mouth region; and detect the expression of the user by using a reference point, a length of a long axis and a length of a short axis of the closed curve of the eye region and the closed curve of the mouth region, wherein the reference point is an intersection point of the long axis and the short axis.