To provide a door opening and closing system allowing even an aged person and a physically handicapped person to open and close a door simply while utilizing advantage of manual operation by a simple configuration and having excellent operation property and ease of use.

This door opening and closing system is provided with a lock for locking and unlocking the door by manual operation using a key and a thumbturn, a door opening and closing mechanism for opening and closing the door by operation of the lock while the lock is unlocked, and a control means for operating the door opening and closing mechanism when the lock is unlocked by manual operation to open the door. The control means operates the door opening and closing mechanism in the direction of closing when the door in an opened condition is moved by predetermined amount by manual operation to close the door automatically.