Security-reinforced door lock, and gate security management system using same door lock

The present invention relates to a security-reinforced door lock, the security of which is reinforced, and a gate security management system using the same door lock, wherein: a double-unlock function using a security code stored in a user portable terminal, and a password input by a user's keystrokes may be provided so as to enhance user convenience; after a user enters or exits using a security code, the door lock itself may update the security code and the password together, generate multiple different passwords, and restrict the reuse of a single-used password or permit the reuse thereof only within a predetermined time, so as to allow the entry or exit of people who do not own a terminal in which a security code is stored, and prevent the leakage of the password; and multiple-visitor management for a door lock installed at a facility as well as a door lock for a single-woman household can be facilitated, and high security can be provided.