1. A method of certifying a user by using a learning system, the method comprising: in response to a reference image being registered, analyzing the reference image by using the learning system to detect characteristic information; storing the detected characteristic information as reference information; analyzing a user image, acquired by photographing a user, by using the learning system to detect face characteristic information and additional information of the user; comparing the face characteristic information of the user and the additional information of the user with the stored reference information, the reference information comprising reference face characteristic information about the face of the user and reference additional information for identifying additional characteristics of the user other than the face of the user; and certifying the user based on a result of the comparing, wherein the certifying the user comprises: in response to reference face characteristic information having a similarity to the face characteristic information of the user that is greater than or equal to a first threshold value and resulting from searching the stored reference information, certifying a person matching the searched reference face characteristic information as the same person as the user, in response to a plurality of pieces of the reference face characteristic information being searched, comparing the additional information of the user with reference additional information corresponding to the searched reference face characteristic information, and in response to reference additional information having a similarity to the additional information of the user that is greater than or equal to a second threshold value being found, certifying a person matching the searched reference face characteristic information as the same person as the user.