1. A method for tagging identification information of a first person to a first digital data created by using a digital equipment in a digital data management system, wherein the digital data management system includes both identification information and life pattern information of a user who creates a plurality of digital data by using the digital equipment, and the first digital data includes an image of the first person, the method comprising the steps of: (a) identifying the first person by using at least one out of additional information of the first person; and (b) automatically attaching the identification information of the first person to the first digital data, wherein the additional information includes at least one of information: information which indicates that if a first digital data group includes an image of a second person, a probability that the first person is determined to be the second person is increased, the first digital data group being comprised of the first digital data and other digital data distributed in a same cluster as that including the first digital data, information which indicates that if the first digital data is created while two or more people have a meeting, a probability that the image of the first person is of a transmitter or a receiver of communication made before the meeting is increased, information which indicates that if an image of a third person is included m times in a second digital data group, a probability that the first person is the same as the third person increases as the number of the m increases, the second digital data group being comprised of the first digital data and other digital data, the m being a natural number, information associated with the first person acquired by using at least one of a time when the first digital data is created and a place where the first digital data is created as well as the life pattern information of the user of the digital equipment, information which indicates that a probability of the first person being determined to be a specific person is varied according to a position and a size of a face of the first person on the image of the first person, information which indicates that if the digital equipment is a dual camera and the first digital data is created through a lens of the dual camera directed toward the user, a probability that the first person is determined to be the user of the digital equipment is increased, and information which indicates that if the digital equipment is the dual camera and the first digital data is created through a lens of the dual camera directed toward the opposite side of the user, a probability that the first person is determined to be the user of the digital equipment is decreased.