Integrated authentication system using electronic contract

The present invention relates to an integrated system which manages the conclusion of an electronic contract by allowing a concluded electronic contract in a mobile terminal to be transmitted to and received from an integrated authentication server, and the integrated system comprises: an electronic contract used when concluding an electronic electronic; a mobile terminal which downloads the electronic contract from an integrated authentication server to conclude a contract and transmits a concluded electronic contract to the integrated authentication server; and the integrated authentication server which transmits the electronic contract to the mobile terminal, receives the concluded electronic contract from the mobile terminal, and integratedly manages the conclusions of electronic contracts, wherein the integrated authentication server comprises: a form design unit which draws up the electronic contract by imaging a contract desired to be concluded by a concerned person, and designs the form of the electronic contract by imaging a contract desired to be concluded by the person concerned, and designs the form of the electronic contract; an authentication unit which manages logins by authenticating the mobile terminal and a user; a form transmission unit which transmits the electronic contract designed by the form design unit to the mobile terminal; and a forgery and alteration checking unit which checks whether or not the electronic contract concluded by the mobile terminal has been forged or altered.