To provide a small and inexpensive door driving device which can reduce control force to be required when a user opens a door rotatably supported to a vehicle body.

A door driving device 20 comprises: a latch mechanism 30 for locking a door 10 at a fully closed position; an operator CT which outputs a signal representing that the door 10 is opened; a control unit ECU which drives an actuator in response to the signal; a rod 41 which goes back and forth to the door 10 in accordance with rotation of the door 10; and a lever mechanism 60 which is driven by the actuator, rotates the door 10 from the fully closed position to the outside of a passenger compartment to locate the door 10 at a predetermined rotating position by engaging into the rod 41 to energize the rod 41 after releasing lock of the door 10 by engaging into the latch 30, and constituted so that engagement with the rod 41 is released when external force for further rotating the door 10 to the outside of the passenger compartment is added to the door 10 at a state that the door 10 is at the predetermined rotating position.