Vehicle back door device with damper stay storage structure

A back door device comprising:

• a hinge, which is provided on a roof of a vehicle;
• a back door, which is configured to pivot vertically about the hinge to selectively open and close a door opening provided at a rear end of the vehicle;
• and
• a damper stay, which urges the back door in an opening direction, wherein
• the hinge is arranged at a position forward of a rear edge of the roof,
• the back door includes a back door rear end portion and a back door roof portion, wherein, when the back door is closed, the back door rear end portion forms at least a part of the rear end of the vehicle and the back door roof portion covers a part of the roof that is rearward of the hinge,
• the back door roof portion includes a storage projection, which projects upward from an upper surface of the back door roof portion such that the storage projection is capable of storing therein the damper stay,
• the damper stay includes a first end, which is connected to the roof at a position rearward of the hinge, and a second end, which is connected to an inner wall of the storage projection, and
• when the back door is closed, the damper stay is stored in the storage projection.