A front side door 2 has an inner panel 12 and an outer panel disposed on an outer side than the inner panel 12 in a vehicle width direction. A door mirror is disposed on the vehicle exterior side of the outer panel, and a base member 30 is disposed on the vehicle interior side of the door mirror with the outer panel interposed therebetween, the door mirror being mounted to the base member. The base member 30 is joined to the inner panel 12.