To provide a door opening and closing system capable of automatically stepwise opening a door up to a fully opening position by a simple configuration and allowing even an aged person and a physically handicapped person to have excellent operation property and safety.

This door opening and closing system is provided with an electric lock for locking and unlocking a door, a door opening and closing mechanism for opening and closing the door by operation of the electric lock while the electric lock is unlocked, and a control means for unlocking the electric lock when a door opening signal is inputted by operator's operation and operating the door opening and closing mechanism in accordance with an operation signal of an operator to open and close the door stepwise. The door is opened and closed at three steps including, for example, 40 degrees, 75 degrees, and 90 degrees.