Side door structure of vehicle

A two-way opening side door structure of a vehicle of which side openings are covered by a front door and a rear door includes a door hinge located at a front end of the front door for swingably supporting the front door, a door hinge located at a rear end of the rear door for swingably supporting the rear door, and an assisting device including a door checker for assisting a vehicle occupant in closing the rear door.