A door outer panel (2) defines a lower edge of a door window section (8). A waist outer reinforcement (4) is placed along the lower edge of the door window section (8), on the inner side, in the lateral direction of the vehicle, of the door outer panel (2), and is fixed to a surface on the inner side, in the lateral direction of the vehicle, of the door outer panel (2). A door beam (5) is placed in the front-rear direction, below the waist outer reinforcement (4), and is fixed to a surface on the inner side, in the lateral direction of the vehicle, of the door outer panel (2). A mirror support stay is placed on the outer side, in the lateral direction of the vehicle, of the door outer panel (2) and supports a mirror. A mirror installation member (30) is fixed to and interconnects both the forward end of the waist outer reinforcement (4) and the forward end of the door beam (5) while straddling between them and supports the lower end side of the mirror support stay.